You’ve never read a book like this before.

I’m going to repeat that, with a bit more emphasis, because that phrase is so misused and overused that it’s become nearly meaningless, and I’d normally avoid it for that reason, except that in the case of S., a book conceived by JJ Abrams and authored by Doug Dorst, it’s actually true:

YOU’VE NEVER READ A BOOK LIKE THIS BEFORE.

Consider, for a moment, the physical form of S.: it comes packaged in a sleek black slipcase, the book’s title glossily emblazoned on the front. Inside is a hardcover book, but not the book, perhaps, you were expecting—this is what appears to be a beaten-up library book called Ship of Theseus by someone you’ve never heard of named V.M. Straka. Puzzled, you open the book and page through, only to discover that it has already been thoroughly worked-over by two readers who’ve marked up nearly every page and left scraps of this and that—newspaper clippings, postcards, even a map scribbled on a napkin—tucked neatly inside.

This, then, is S.—not a book, per se, but a story told by a found object: a fictional book, by a fictional author, translated by a fictional translator, and read by two fictional readers.

As for the story itself—well, where to begin? I suppose the best place would be with V.M. Straka, the author of Ship of Theseus, and the mystery man around which the experience of S. revolves. Who was Straka? A novelist, yes, but also an anarchist, an anticapitalist political agitator, rumored by some to be a terrorist and an assassin. Much of his life was spent in hiding from rich and powerful enemies; even the name “Straka” might be a fake, and there’s rampant speculation among scholars about who the “real” Straka might be—if indeed there is one.

We learn all these details in a Foreword by Straka’s translator, F.X. Caldeira. This Foreword also reveals that Straka went missing in the process of transmitting the manuscript of Ship of Theseus to Caldeira, and that the translator has taken it upon himself to finish the final, incomplete chapter based on what he believes to be the author’s wishes. Caldeira comes back from time to time throughout the book to offer his thoughts in a footnote—he seems to think that the novel, which tells the story of an amnesiac named S. who falls in with a group of leftist revolutionaries, may contain some key to Straka’s true identity and the fate that befell him. Or maybe Caldeira and Straka are one and the same, and the footnotes are just a clever put-on to keep people guessing.

Feeling dizzy yet? Try to keep up—I haven’t even gotten to the readers yet. Their names are Jen and Eric: she’s an undergrad working at the library, and he’s a grad student doing his dissertation on Straka. In marginal notes and pieces of paper passed back and forth, they speculate on the various mysteries surrounding Straka—Who was he? Who killed him, if indeed he was killed? Just how autobiographical is Ship of Theseus, really? Was Straka revealing his true self in the pages of the novel, or trying to throw his enemies off the trail? Jen and Eric also strike up a sort of friendship rooted in their mutual love of books, a relationship that begins to show the potential of blooming into something more.

I realize that this description makes S. sound like a bit of a chore. But it is so not a chore. If S. requires a bit more active energy than a more conventional book does, it’s energy that I found myself willing, even eager, to spend. The world of the book wasn’t a difficult one to fall into, and when I wasn’t reading I found myself eager to return to its pages. The thrill of making a connection, of finding a clue that clarified some things while revealing even further mysteries, was all I needed to keep me moving forward.

It also helps that the story is completely compelling on every level. Even without the apparatus of footnotes and marginalia, Ship of Theseus is a compelling read on its own, a bizarre and portentous adventure story of the kind Jorge Luis Borges or Italo Calvino might have written. Eric and Jen’s story mostly focuses on more prosaic matters, like workstudy jobs and dissertation advisors and lots of agonizing about what each of them wants to do with their lives—and, of course, analyzing the text they have in front of them. Soon, though, their storyline begins to take on a more sinister tone, as they begin to see signs that whatever agency killed Straka might still be at work in the present day.

It’s a complex little puzzle of a book—even the title of Straka’s novel, Ship of Theseus, is a brain-teaser. It’s a reference to Theseus’s paradox, a though experiment asking whether a ship that has had all its parts replaced is still the same object. That, plus secret codes in the footnotes, and a list of characters so long you’ll want to keep a pen and paper handy, might open S. up to the critique that’s it’s all brain and no heart. Puzzles are all well and good when you’re working on them, but when’s the last time you fondly recalled your favorite crossword? Curled up with a beloved Sudoku from when you were younger?

It’s a valid concern—and an unfounded one, happily. S. is a puzzle, yes. But it’s a puzzle that packs a resonant punch, revealing shades of unexpected meaning even after all its mysteries have been solved. The emotional heart of S. is revealed in the allusion to the Theseus paradox: it’s the question of what a person ultimately is, what a life really consists of when all its pieces have been worn away by time. Who is a man who can’t even remember his own name? If he dies never remembering, never understanding what his story was all about, what did his life really mean? Should Eric finish that dissertation? Should Jen take that marketing internship? Who are they? What do they want? Do they love each other?

Does it matter?

These are the questions that are still sticking with me today. That, and the feeling of utter delight I felt while reading S., the feeling of having discovered something truly original, something that seemed keyed to my own private symbolic language, to readerly desires I didn’t even know existed. The feeling of losing myself, of discovering myself—like Eric and Jen, who lost themselves and found each other—in the pages of a book.