“S,” the new mystery novel by J. J. Abrams and Doug Dorst, may be the best-looking book I’ve ever seen. From the outside, it looks like an old library book, called “Ship of Theseus” and published, in 1949, by V. M. Straka (a fictitious author). Open it up, though, and you see that the real story unfolds in Straka’s margins, where two readers, Eric and Jen, have left notes for each other. Between the pages, they’ve slipped postcards, photographs, newspaper clippings, letters—even a hand-drawn map written on a napkin from a coffee shop.

To solve the book’s central mystery—who is V. M. Straka, really, and what does he have to do with Eric’s sinister dissertation advisor?—you have to read not just “Ship of Theseus,” but all of Jen and Eric’s handwritten notes. The book is so perfectly realized that it’s easy to fall under its spell. The other morning, I was so engrossed in a letter from Jen that I missed my subway stop. (The letter, handwritten on Pollard State University Library stationery, marked a turning point in Eric and Jen’s flirty, romantic relationship.)

“S” is the unusual result of a collaboration between two unusual people. Abrams has written, created, produced, or directed dozens of films and television shows, including “Felicity,” “Alias,” “Lost,” “Fringe,” “Person of Interest,” and two “Mission: Impossible” films; he’s currently directing the new “Star Wars” movie, which comes out in 2015. Meanwhile, Dorst’s previous novel, “Alive in Necropolis,” was a runner-up for the 2009 Hemingway Foundation/PEN Award; he’s also won “Jeopardy!” three times. If you want to write a romantic mystery meta-novel in which two bibliophiles investigate the conspiracy around an enigmatic Eastern European author, you couldn’t choose a better team. Tonight—Saturday, November 23rd—Dorst and Abrams will be talking about “S” with Lena Dunham, at Symphony Space; I spoke with them over the phone earlier this week.

What could possibly have inspired you to produce a book like “S”?

Abrams: The idea came to me when I was at the airport. I saw a paperback novel sitting on a bench, and I went to pick it up. Inside, someone had written, in pen, “To whomever finds this book—please read it, take it somewhere, and leave it for someone else to find it.” It made me smile, this optimistic, romantic idea that you could leave a book with a message for someone. It reminded me of being in college, and seeing the notes that people would leave in the margins of the books they’d checked out of the library.

And then, I started to think: what if there were a very cool book that was completely annotated—just covered in marginalia and notes between two people? And—what if a conversation, or a relationship, began inside a book? That was the beginning of the process, maybe fifteen years ago.

How did Doug get involved?

Abrams: I told Lindsey Weber, who works on features with me at Bad Robot [Abrams’s production company], about the idea; she got excited about it. We weren’t sure if the novel itself should be a new novel, or a preëxisting novel. Then Lindsey found Doug. He came in, and we pitched the idea to him, and he ran with it.

Dorst: It was around the summer of 2009—they handed me the concept and said: “What kind of story would you tell, given this conceit?” And, first of all, I got really excited, because of the challenge of telling a story in this really restricted form. That really appealed to me as a writer. As far as the substance of the story, I was reading a book on the Shakespeare question at the time, and that sent me over into reading about the B. Traven controversy. I started thinking that, if the notion of a book is central to this idea, what if there were a mystery about its author? It seemed like it would be really, really fun to make up an entire bibliography and history about this writer. From there, it was a small step to deciding that the people who are reading the book should be book geeks themselves.

How did the collaboration work? And Doug, how did you keep the story straight? Did you use a whiteboard? Did you write “Ship of Theseus” and the marginalia at the same time, or separately?

Dorst: I would’ve been well-served if I’d had a whiteboard, but I’m a fundamentally disorganized person, and I had nothing resembling an organizational system! I wrote “Ship of Theseus” first, all the way through—everyone agreed that it really had to be able to stand on its own—and then I layered in the marginal notes. A lot of it was trial and error. But I’m a writer; I like making stuff up. This was, basically, an infinite sandbox of joy and fun. There was really no end to the world-building, the history-shaping that could be done, especially since J. J. and Lindsey were really encouraging every ludicrous impulse I had to make things bigger and more complex. At any given moment, I’m asking myself, “Why stop?”

Abrams: It was, frankly, not unlike developing a screenplay. There were outlines and pitches at the beginning, then early chapters. Lindsey would often work with Doug, and then show me stuff. It was especially fun, though, because the final product wasn’t a script that then needed to be cast and shot and edited. It was the text. And then we worked with a design firm, Melcher Media, who helped make it what it is.

You must be pleased with how the book has turned out, from a design perspective.

Abrams: It’s intended to be a celebration of the analog, of the physical object. In this moment of e-mails, and texting, and everything moving into the cloud, in an intangible way, it’s intentionally tangible. We wanted to include things you can actually hold in your hand: postcards, Xeroxes, legal-pad pages, pages from the school newspaper, a map on a napkin.

One of the most arresting aspects of “S” is the handwriting. I can’t remember when I last read so much of someone’s handwriting. And the language in which the handwritten letters and notes are written feels very natural in its cadences. You feel like you’re snooping on something intimate.

Dorst: That’s exactly the illusion that we wanted to create. We had been talking about the intimacies of books and about the intimacies that might come from sharing a book; these are two people who are building intimacy, and handwriting is another way that that intimacy can be developed and expressed. The designers chose the people who did the handwriting very carefully. And the writing’s not actually the same all the way through—it changes as the characters change.

“S” is reminiscent of older novels. It’s a little Nabokovian. It reminded me of an epistolary novel, too—many epistolary novels present the letters as “found” objects.

Abrams: There are a number of books that influenced us, some in that tradition of “faux-discovery,” and others that are more overtly games. For instance, there are these great mysteries by the British writer Dennis Wheatley. They’re packed with ripped-up photographs and little waxed-paper evidence envelopes and found letters and a lock of hair. And then the answer to the mystery was in a sealed document in the back. Only when you felt like you understood the whole whodunit would you cut open the seal and read.

“S” is more character-driven than that, though. It’s not really a whodunit.

Abrams: No. With “S,” our idea was not to create, you know, a kind of diabolical sudoku. The fun was in creating something that was simultaneously emotional and sweet and romantic and serious and suspenseful and scary and maybe even confusing in places—and which was, ultimately, an immersive experience, something that would be fun for people to get into and discover.

Dorst: I wanted to try to capture a sense of wonder. I hope that there’s a lot of wonder in “S.” It’s about the wonder of discovering a book. But it’s also about the wonder of discovering another person—the wonder that comes from feeling yourself getting to this place where your life is about to change, in a big way. If “S” happens to evoke that feeling in people, that would thrill me.