Recommendation
MM sci-fi romance
The alien books are filthy. The ones with two humans on a spaceship barely kiss. Same genre, same shelf, and nothing on the cover warns you which you've picked up.
It comes down to who published it. Romance houses do the aliens and they don't hold back. Science fiction houses do the ships and they shut the door.
Updated 29 August 2026
The three kinds, and what each one gets you
Work out which you're after and the rest follows:
- Near-future Earth. The technology has arrived and the book is about what it did to people. Heat anywhere from a single kiss to as explicit as the genre gets.
- Out in space, humans only. Ships, politics, long missions, and closed door.
- Aliens. One of them isn't human, and it's explicit.
- Heat and ending stated plainly for every book. You shouldn't have to find out at chapter twenty.
What the heat ratings mean
The five point scale romance readers already use, lowest to highest. Every book below is marked on it.
- Glimpses and kisses a kiss at most, and no sex on or off the page
- Behind closed doors it happens, but the door shuts first
- Open door at least one scene you are in the room for, written without the explicit words
- Explicit open door two or more scenes, explicit, and a range of things happening
- Explicit and plentiful several explicit scenes spread through the book
Near-future Earth
Close enough to now that you can see how we got there.
Docile
AboutElisha Wilder signs himself over to clear what his family owes. The man who buys the contract is Alexander Bishop III, whose family manufactures Dociline, the drug that makes an arrangement like this bearable. Elisha watched what it did to his mother and refuses to take it, so he is awake for all of it.
Read it ifYou want the one that doesn't look away, and you want the money to be the villain.
DifferentConsent is the subject, not a content note. Elisha can't meaningfully refuse for most of it.
SettingMaryland, and a family debt of three million dollars
HeatExplicit and plentiful - 5 of 5 on romance.io
EndingThey end up together, and the argument is whether the book earned it.
SeriesStandalone.
Rating3.39 on Goodreads, from 4,941 ratings
Fun factThe cover puts its thesis under the title: no consent under capitalism.
Untitled gene-splice novel
Not written yet
Untitled gene-splice novel
AboutEveryone with money edits their children, and a cap keeps them looking human. The only legal way past the cap is a corporate contract: a company pays for the modification and owns the labour it built the child for. He was spliced for the mine before he was born. So was the heir who falls for him, illegally, and nobody has ever come after that family for it.
DifferentThe ones who look least human are the ones whose labour was sold before they could object to it, so you can read class straight off the body. Each book is a different couple in the same world.
SettingA near future where editing your child before birth is ordinary, if you can pay for it
HeatExplicit and plentiful
The Bones Beneath My Skin
AboutNate Cartwright has lost his parents, his job and his brother, so he drives out to the family cabin with nowhere better to be. Two people are already living in it: an ex-Marine called Alex Weir, and a girl who calls herself Artemis Darth Vader. She isn't a girl and she isn't human, and both the government and a group of cultists want her back.
Read it ifYou want found family that costs something, and Klune with the sweetness turned right down.
DifferentThe romance shares the book with a child and a chase, so Nate and Alex get less room than a straight romance would give them. It barely feels like science fiction either: 1995 Oregon, motels and payphones, with one impossible thing in the middle of it.
SettingA family cabin outside Roseland, Oregon, spring 1995
HeatOpen door - 3 of 5 on romance.io
EndingHappy, with a bad stretch before it. The epilogue is where the payoff sits.
SeriesStandalone.
Rating4.07 on Goodreads, from 50,268 ratings
Fun factIt came out in 2018, two years before The House in the Cerulean Sea. That book made Klune's name and this one was reissued on the back of it.
All That's Left in the World
AboutAndrew turns up at Jamie's door injured and starving, and Jamie takes him in because there's nobody left to say no. They get comfortable. Then the shelter is breached and the two of them head south looking for anyone still organised, and Andrew's account of how he got there keeps not quite adding up.
Read it ifYou want it gentle, and you want two boys walking rather than a war.
DifferentYoung adult and it reads it. A kiss is as far as it goes. The pathogen is background rather than plot: this is two people talking while they walk, and the danger is other survivors.
SettingA house in the Pennsylvania woods, after a pathogen took nearly everyone
HeatGlimpses and kisses - 1 of 5 on romance.io
EndingHFN. Hopeful rather than settled, and the world is still hostile when it closes.
SeriesFirst of two. The Only Light Left Burning follows.
Rating4.21 on Goodreads, from 45,195 ratings
Out in space, humans only
Humans only, a long way from home, and the door stays shut.
Winter's Orbit
AboutPrince Kiem is the embarrassing one the family keeps at arm's length. Count Jainan is the widower of the cousin who died, and the treaty needs him married again immediately, so the two of them are handed to each other. Jainan's first marriage turns out to be the thing neither man can talk about, and the treaty turns out to depend on what actually happened in it.
Read it ifYou want arranged marriage done properly, and you don't need the door open to feel it.
DifferentThe politics is real and the mystery takes real room, so it's a treaty thriller with a marriage inside it as much as the reverse. Jainan's first marriage was five years of domestic abuse, verbal and physical, shown on the page in flashback and handled with real care. It's the reason the slow burn is slow, and the reason to read the content notes.
SettingThe Iskat Empire, and a marriage arranged inside a week
HeatBehind closed doors - 2 of 5 on romance.io
EndingHEA, and it finishes here.
SeriesStandalone. Ocean's Echo is a separate story in the same universe.
Rating3.97 on Goodreads, from 28,430 ratings
Fun factMaxwell shuts the door in both of the books she has set in this universe.
The Darkness Outside Us
AboutAmbrose Cusk wakes on a ship he doesn't remember boarding, sent to rescue his sister from a crashed mission. His only crewmate is Kodiak Celius, from the rival power, who has barricaded himself in a compartment. The ship's computer speaks in Ambrose's mother's voice, and there's evidence that other people have been aboard.
Read it ifYou want the twist, and you're happy for the romance to sit inside a puzzle rather than the other way round.
DifferentIt turns on a reveal partway through, and the back half is a different book. Nothing here will tell you what the reveal is. Young adult, closed door, and considerably heavier than the cover suggests.
SettingThe Coordinated Endeavour, on its way to Titan
HeatBehind closed doors - 2 of 5 on romance.io
EndingA happy ending of a kind. They get a life together, and it isn't the life either of them set out for.
SeriesFirst of two. The Brightness Between Us followed in 2024.
Rating4.31 on Goodreads, from 34,632 ratings
Fun factA Stonewall Honor book, which is the American Library Association's award for LGBTQ writing.
Aliens
One of them isn't human. Expect it explicit.
That Alien Feeling
AboutPrince Harht'ngh'chaali is banished to Earth by his parents, takes the name Harry, and tries to pass for human. He wears terrible shirts and flowers in his hair and has a kind word for everyone. Adam Crawford has money and looks and no intention of falling for anybody. He falls hard for the odd man at the coffee shop near his office.
Read it ifYou want the sweet one, and you want the alien to be genuinely odd rather than a human with a backstory.
DifferentThe obstacle is species rather than anything either man does, so there's no villain and no third act betrayal to sit through. What's in the way is simply that he isn't from here.
SettingA coffee shop, and a planet half a galaxy away
HeatExplicit open door - 4 of 5 on romance.io
EndingHEA.
SeriesFirst of five Calluvia's Royalty books.
Rating3.98 on Goodreads, from 10,670 ratings
Fun factHazard's other long-running series, Straight Guys, is contemporary rather than science fiction.
Dark Space
AboutEarth conscripts every boy at sixteen and posts him to a station. Brady Garrett is angry, homesick, and can't go home except in a bag. Cameron Rushton was taken by the aliens four years ago and has just been returned. The doctors botch bringing him out of stasis, and Brady gets wired to him as a stopgap. The two of them start sharing thoughts, memories and dreams.
Read it ifYou want it bleak, and you want the telepathy to cost somebody something.
DifferentGrim by design. The content notes run long and cover things done to both men that neither agreed to, along with torture and a war being lost. The bond means Brady has no privacy from Cameron at all, and the book treats that as a problem rather than as a romantic device.
SettingDefender Three, a station between Earth and the Faceless
HeatExplicit open door - 4 of 5 on romance.io
EndingHFN, and no cliffhanger, after a brutal last act.
SeriesFirst of three. Darker Space then Starlight, and neither of those ends on a cliffhanger either.
Rating4.02 on Goodreads, from 5,787 ratings
Fun factLisa Henry lives in tropical North Queensland, so this is an Australian book about the end of the world in space.
Claimings, Tails, and Other Alien Artifacts
AboutLiam is a human linguist who trades on the Rownt homeworld, and since the war he has wanted a small quiet life and nothing else. Ondry is the best trader the Rownt have. Ondry works out that Liam is hurt and claims him, which is what a Rownt does about somebody worth keeping.
Read it ifYou want the alien to stay alien, and you want two men working out what the other one is even offering.
DifferentLiam is submissive and has spent his life hiding it, because every time he has shown it somebody has hurt him for it. The Rownt treat a submissive as the most valuable thing a person can be given, so Ondry isn't putting up with it. He's delighted.
SettingPrarownt, where humans trade and mostly misunderstand
HeatExplicit open door - 4 of 5 on romance.io
EndingHEA.
SeriesFirst of five Claimings books. Gala wrote the prequel afterwards, Prelude to Claimings, Tails, and Other Alien Artifacts.
Rating3.96 on Goodreads, from 5,120 ratings
The 5th Gender
AboutThe galoi have five genders, purple skin, no interest in outsiders and no word for murder. Then there's a body on one of their ships, so they have to hire a human. Detective Drey Hastion gets the case, and gets Tristol with it: a galoi delighted by everything and everyone. Drey has already decided that somebody like that would never want somebody like him.
Read it ifYou want a murder mystery where the romance is carried by an alien being relentlessly cheerful at a grumpy man.
DifferentThe five genders are a fact about the species with consequences for the plot rather than a label on the blurb. It's also short and much lighter than the cover suggests.
SettingA galoi ship, and a murder nobody aboard has a word for
HeatExplicit open door - 4 of 5 on romance.io
EndingHEA.
SeriesSecond of five Tinkered Stars books, and it reads alone. Crudrat came first and is a different story entirely.
Rating4.16 on Goodreads, from 3,591 ratings
Fun factG.L. Carriger is Gail Carriger, and the cover says so: the Parasol Protectorate books go out under her name and the explicit ones under initials.
Frequently asked questions
How much MM sci-fi romance is there?
More than you'd think and it's badly indexed. The Goodreads MM off-world list runs to 163 books and the alien list to 100, and once you dedupe them against the yearly lists you get 243. What there isn't is anybody sorting them, which is why the same four titles come back every time somebody asks.
Which MM sci-fi romance should I read first?
Winter's Orbit if you want arranged marriage and politics and don't need heat. The Darkness Outside Us if you want to be got at by a twist. Claimings if you want the alien to feel genuinely alien. Docile only if you've read what it's about and want it anyway.
Why is all the alien romance explicit and all the space opera closed door?
Nobody planned it. Alien romance is published as romance, where explicit is the house style. Humans-only space fiction is published as science fiction, where it isn't. Each side brought its own habits and the shelf label never caught up, so a rating tells you nothing about which one you've picked up.
Is any of it Australian?
Lisa Henry, who wrote Dark Space, lives in tropical North Queensland and has been publishing MM since 2012. She's on the Australian guide too. Beyond her the shelf is overwhelmingly American, which is the same pattern as almost every subgenre here.