Two well-known novels answer to "pen pal book". This guide is mostly about the first: Penpal, by Dathan Auerbach, a slow-burn horror novel that began in 2011 as a run of posts on Reddit, was funded by its readers on Kickstarter, was self-published in 2012, and has kept turning up on horror BookTok.
The other is J.T. Geissinger's Pen Pal, a dark romance. If a letter from a prisoner is what you had in mind, it's further down. Everything on this page is spoiler-free, and with Penpal that matters more than usual.
What Penpal is
It begins in kindergarten. A class ties letters to helium balloons and lets them go, hoping someone, somewhere, will find one and write back, and as replies come in, the teacher marks on a map how far each balloon went. It is a gentle opening for a horror novel, which is rather the point.
The man telling the story is grown now, and trying to make sense of strange, frightening things from his early childhood, things whose truth his mother has kept from him. He doesn't tell them in order. He goes back to one episode, then another, years apart, and incidents that seemed to have nothing to do with each other slowly start to look like pieces of one story.
The title can mislead you: Penpal is not told in letters. The pen pals of the title come from that balloon project. The book itself is first-person recollection in six parts, each set at a different point in the narrator's childhood and each keeping the title of the Reddit post it grew from: Footsteps, Balloons, Boxes, Maps, Screens, Friends. Wikipedia calls it a horror-suspense novel, which is about right: slow-burn, with its roots in creepypasta, the internet's campfire stories.
Where it came from
In the autumn of 2011, a Reddit user called 1000Vultures posted a story called "Footsteps" to r/nosleep, a forum where horror stories are posted as if they really happened and readers play along. He had meant it as a standalone story. Readers asked for more, five more followed, and before the year was out The NoSleep Podcast had adapted the stories for its first season.
In April 2012, Auerbach, the writer behind 1000Vultures, went to Kickstarter to turn the stories into a novel, with a goal of $1,500. In a month, readers put in more than $15,000, over ten times what he had asked for. He revised, connected and expanded the six stories into one book and published it himself that year, under his own imprint, also called 1000Vultures.
Film rights were optioned in 2012, and no film has been announced since. As far as we can find, the book has only ever been published in English.
Why it's on BookTok
The Penpal videos we found run from 2023 into 2025: reviews, recommendations in the you-need-to-read-this register, and a horror BookTok account sharing a clip of its interview with Auerbach, whom it calls the "author of the iconic Penpal". On Goodreads the book has close to 70,000 ratings.
It suits the format for reasons that need no plot. The story behind the book is almost as good as the book: a Reddit post its readers paid to turn into a novel. It is short, about 240 pages in paperback. And it is best started knowing almost nothing, which suits a short video that says, more or less, trust me. If you are going to read it, read it before you read anything else about it, including its Wikipedia page and the comments under those videos.
The other Pen Pals
Pen Pal — J.T. Geissinger (2022). The other big one, and a very different book: dark romance, not horror. On the day a widow buries her husband, a letter arrives from a man in a state penitentiary she has never met, and the letters grow intimate. Its publishers call it a BookTok sensation, and it has more than three times as many Goodreads ratings as Auerbach's. It has explicit sexual content, and the publisher lists content warnings. It is also the one that has been translated: in Brazil it's Pen Pal (Editora Arqueiro), in Portugal Além das Palavras, in Italy Ti aspetterò per sempre, in France Le prisonnier. If a friend abroad told you about "the pen pal book", it may well be this one.
Pen Pals — Alexandra Pichard (2017). A picture book. Oscar the ant and Bill the octopus become pen pals through school, and their whole story is told in the letters they send each other.
Pen Pal — Francesca Forrest (2013). A twelve-year-old in a floating community off the Gulf Coast sends a message in a bottle, and it reaches a political activist imprisoned above a lake of molten lava. Told through letters, journal entries, news articles and secret government memos.
Dear Pen Pal — Heather Vogel Frederick (2009). The third Mother-Daughter Book Club novel, for younger readers: the club reads Daddy-Long-Legs, and the girls are set up as pen pals with another mother-daughter club in Wyoming.
Nine books like Penpal
Not all of these are told in letters, and Penpal isn't either. What they share is a story that reaches you in pieces (diaries, drawings, records, other people's paperwork), so you do some of the assembling yourself.
Strange Pictures — Uketsu (2022; in English 2025, tr. Jim Rion). The closest in shape. Several eerie stories, each built around drawings, that seem separate until they connect at the end. It has sold more than 1.5 million copies and been translated into more than thirty languages, so there is a fair chance you can read it in yours.
A Head Full of Ghosts — Paul Tremblay (2015). A woman looks back on the time her family let a reality TV show film her fourteen-year-old sister's apparent possession. Her account, given to an author writing a book about it, alternates with a blogger's posts about the show, so you keep weighing what she remembers against what was recorded. It won the Bram Stoker Award for Novel.
Dracula — Bram Stoker (1897). The great-grandparent of horror told in documents: letters, diaries, newspaper cuttings, a ship's log. Frightened people piecing together what is happening to them, one record at a time.
Carrie — Stephen King (1974). King's first novel. The story is cut with reports and excerpts, arranged roughly in order, as if a whole town were still trying to explain what happened. King invented many of those documents to stretch what began as a short story to novel length, which is one more thing it shares with Penpal.
House of Leaves — Mark Z. Danielewski (2000). A family finds that their house is larger on the inside than on the outside. The account comes as a manuscript recovered after its author's death, buried in footnotes and accompanied by letters from the finder's mother, on pages you sometimes have to rotate to read. It is most often described as horror. For readers who liked the digging.
We Need to Talk About Kevin — Lionel Shriver (2003). Told in letters from a mother to her husband as she tries to understand their son. It won the 2005 Orange Prize. Another unsettling look back at a childhood, this time from the parent's side of the table. Content note: it centres on a school killing.
Annihilation — Jeff VanderMeer (2014). A biologist's field journal from the twelfth expedition into Area X, a stretch of coast closed to the public for decades, where earlier expeditions ended badly. Slow, creeping, ambiguous dread, in a first-person written record. It won the Nebula and the Shirley Jackson Award.
Devolution — Max Brooks (2020). A remote eco-community in the Pacific Northwest is cut off when Mount Rainier erupts. The story comes mostly from one resident's recovered journal, with interviews and research between the entries. Its trick is the one Penpal's r/nosleep roots rely on: making the unbelievable feel documented.
The Appeal — Janice Hallett (2021). A murder mystery told in emails, messages, letters and documents, which two young lawyers have to sift through, and so do you. For readers who liked the puzzle more than the scares.
If it's more Auerbach you want, his second novel, Bad Man (2018), follows a young man still searching, five years on, for the little brother who vanished from a grocery store. It isn't built from documents, but it is the same writer.
If you wanted the other kind of letters
If you typed "pen pal book" hoping for something warm, twelve novels made of letters starts with Virginia Evans's The Correspondent.
And if all this has you wanting to write to a stranger yourself: on Kindredly you're a number instead of a name, with no profile and no photos until you both choose to trade names. A safety check reads letters before they go out to strangers' desks, you can report or block in a tap, and it's for adults only.