When, on his deathbed, Don Quixote renounces his mad quest, Sancho won't have it. Sancho started out a practical peasant who, after adventures with Quixote, became as enchanted as his old friend; he didn't want to then hear that it was all for nothing, that they had both been, as the world had repeatedly told them, fools.

This scene, in my dog-eared copy of Burton Raffel's translation, is underlined in pink highlighter and asterisked in black pen because I read it twice: once in 1996 for a movie version I worked on, and again in 2000 when I began writing my first novel, The True and Outstanding Adventures of the Hunt Sisters. I was writing about my sister because unlike me, she'd always been wildly optimistic and improbably idealistic, and because she had died the year before from leukemia.

I'd worked in the film business for ten years as a studio executive and producer, but my original ambition had been to write. Screenplays were my early failures: I'd been seduced by the seemingly short, dialogue-driven form and also by the widely held and totally false notion that screenwriting was an easy way to get rich. After I became an executive in LA, I continued to write on weekends, but lacking enough faith, I was quickly tempted away from the solitary hard work of it by dinner parties, job offers, green-lit movies. It was always easier to believe in other peoples' dreams than my own.

My sister was 28 years old when she was diagnosed. She responded with a quixotic courage that eventually infected me; during her two-year illness, I'd grown less pessimistic both about her prognosis and about life itself. Her death, like Quixote's, was unexpected, and it left me as confused as Sancho: what was the point of her faith if it wasn't going to save her?

The answer may seem self-evident, but having been a proud cynic and pessimist all my life, I truly didn't possess it. Yet after her death my rather gloomy outlook suddenly seemed like an affront to her defiant spirit; with my "talent for unhappiness," as a friend once described it, I was squandering what she'd fought so hard to hold on to, and lost. My lack of faith and fear about writing now seemed puny and indefensible. I could hear her goading me: You want to write? How badly?

In January 2000 the film I was producing wrapped, and the editing process began in New York City. I was living in an artist friend's studio, a tiny walk-up on the Upper West Side. With a paint-dappled floor and slanted walls, it was smaller than any office I'd had in the film business, but it was cheap: cheap enough that if I was careful, I'd have one year to do nothing but write.

That spring I received in the mail a bulging envelope of old letters my sister and I had written to each other. My mother was in the throes of her annual attic purge and had found them in a box of my old school papers. From camp I complained about mosquito swarms, mushy spaghetti and forced marches; when she was fifteen and I was away at college, my sister declared both her intention of becoming a pop star and her strong opinion that I had better be home for Thanksgiving. There were huge time gaps between letters, so reading them was like piecing together a mystery. A really hot guy, a U.S. history exam, the wish for Bob Seger tickets were all left hanging, unless my memory could fill in the blanks. I read and re-read her letters, the sight of her handwriting somehow comforting me. I also felt the tug of irrational hope that maybe I'd overlooked a letter, that in the envelope I'd find a new one from her, a postcard perhaps, assuring me that she was fine and that heaven in fact was even better than advertised.

Until I read her letters, I'd been struggling with how to shape her story and whether to write a memoir or a novel. I had the usual reams of notes, ideas, questions, incomplete outlines. My experience writing and developing screenplays was so unrewarding that I never considered telling the story as a film. I knew too much about the hard life of a screenplay: its many well-meaning and bossy studio-executive mothers and, later, its bad marriages to and divorces from directors and stars, followed by further desperate courtships; the money worries and serious illnesses that a script suffered through before finally being released into the world as the fully grown film of the screenwriter's idea from long ago. Forget the obstacles to production-the form itself was too restrictive. I wantedwords to count, not plot points, not starring roles, not the number or placement of action set-pieces.

Memoir would also be too confining. My urge was to discover, not to report, and ideally, to be transformed by the process. I already knew what happened; what I didn't know was how to live with it. I needed to create characters, because it's easier to observe just about anyone better than yourself. In new situations my characters could confront things that I never did and say things I would like to have said, or needed to be told. Fiction-writing could provide some wish-fulfillment both for me and, hopefully one day, a reader.

My mother had sent the letters to help me draw the sisters as children, but what they gave me was more important-what Ortega y Gasset calls the "essential grace" of a piece of work: its form. Epistolary novels are about as unfashionable as cassette tapes; unsellable is the word often used to describe them. I had never read one, and I didn't set out to write one. When friends heard I'd put my movie career on hold to write a novel of letters they looked concerned, as if I were as mad to believe in this antiquated form as Don Quixote was to believe in chivalry. Even I resisted the idea of telling the story entirely in letters; it would be difficult to create a sense of what in the movie business we call "action." It would be hard to get around all sides of the story. Initially, I imagined the novel would only be bookended by two letters. Reading my sister's letters was a strangely voyeuristic pleasure, and I imagined a reader could feel that way, as if he'd discovered a trove of letters in the floor of an old house. Each letter would be an intimate, direct address from one character to another, letters that a reader would read essentially over that character's shoulder. There would be none of the artifice of movies, no make-believe of makeup, lights, special effects. In these letters I could come as close to grabbing a friend's lapel and whispering, listen to this, as I could get.

The protagonist, Olivia, was leading me this way so insistently that she didn't even allow other characters to write letters. Olivia is peripatetic-she flies between Los Angeles, London, Madrid, New York, and Ohio-which also suited a narrative built on letters. E-mail has made people comfortable with them; they're not as formal as the ones found in earlier epistolary novels such as Pamela and A Woman of Independent Means. Olivia's letters are casual, confessional, and often furious to the point of being humorous. I found myself writing outrageous letters and comic scenes almost as an antidote to the sadness of the story. A second plot emerged out of that impulse to be funny: Hollywood.

My ten years there were just asking to be satirized. And what better movie for the protagonist to be producing than the impossible dream of Don Quixote? Having worked on an ill-fated film of it myself, I was well-aquainted with its challenges. Thematically, it was a perfect fit. For 400 years, Don Quixote's crazy quest and deathbed apostasy have left readers troubled by the same questions that my sister's defiant optimism and subsequent death had raised in me: Is faith-in God, in your desire to write, in anything uncertain-just a form of delusion? Did Don Quixote know the windmills weren't really giants and charge them for the sheer glorious hell of it?

My sister's letters are in a box under my bed, and from time to time I re-read them, mostly just to see her handwriting on the girly-pink stationery or the fringed lined paper ripped from a spiral notebook. Like Sancho, I couldn't believe that my sister's quest was all for nothing; the story couldn't end that way because she didn't live that way. I still don't fully know the answers to the questions that drove me to write this book, but I'm closer. By writing an epistolary novel about the lunatic faith of a dying young woman and Don Quixote, I think I've absorbed a little of that blessed lunacy myself. Writing demands that kind of faith, and sometimes writing, like life, rewards you with it too.


Excerpt from The True and Outstanding Adventures of the Hunt Sisters:

We also do laps. The nurses say laps are important, and didn't Aristotle say life is movement? Every day around 1 o'clock I drag her out of bed even if she begs me not to. She swings her long sticks to the floor and when I squat to slide on her slippers she hears my knees crack like a fire and says, Livvie, what's wrong with your knees? I place the BMT mask, a white paper disc with a special killer filter in the center, against her steroid-swollen face and as I gently pull the elastic thread over her hairless head I remember shoving her striped red woolen cap on her six year old brown-haired head in the winter and then she places her good hand on my shoulder and pulls herself up and out of bed and we're off, out the door and racing to the toboggan, both calling I get front, and then whooosh down we go down the fresh fallen snow on the hill, tumbling off at the bottom, starting a snowball fight with Jim or making angels or in this case, we shuffle very slowly down the wide open corridor of the BMT wing, and sometimes there is another poor skeletal fuck, tunafish colored, too, shuffling down the promenade in his baggy bathrobe with his IV pole on his arm like a fine dance partner and we decide to overtake him, that miserable old man, that miserable old woman, you can't tell the difference, everyone is old and miserable here, but she's not, she's not, she's 18 getting read for the prom and hissing at me to do her hair right.