Many a woman has fallen in love with a charismatic but unstable man who pops in and out of her life at random intervals.  The title character of Audrey Niffenegger's The Time Traveler's Wife  has this dilemma in spades: when her husband disappears, it's not to the neighborhood bar, but to other decades.

Niffenegger seems to have hit a first novelist's hole in one.  Her upcoming appearance at New Paltz's Ariel Books is part of her third major book tour.  The Time Traveler's Wife is a national best-seller, with reviews that range from respectful to enraptured.  She's appeared on NPR and "The Today Show"; film rights were snapped up by Brad Pitt and Jennifer Aniston.  Niffenegger is a literary rock star, but - as befits someone whose book has a gritty, early-punk soundtrack - a determinedly iconoclastic one.  She's that rarest of phenomena, an indie-label maverick who made it big without selling out.

Although The Time Traveler's Wife is Niffenegger's first mainstream novel, it's not her first book.  Her previous works are visual novels, with letterpress type and aquatint illustrations, printed in limited editions of ten.  "I'm fixated on oddity.  The themes I tend to work with are mutants, peculiar nature things, taxidermy, amputation."  These fixations show up in The Time Traveler's Wife as well, in a different medium.  "Part of the enjoyment and challenge was rendering things in words that I ordinarily do with a picture.  Words are so much more economical.  Even a simple action or gesture takes a long time to draw.  You can convey that in one sentence in a novel, and the reader makes the pictures imaginatively."

Niffenegger was surprised that The Time Traveler's Wife turned out to be so long.  "I always thought of myself as a sprinter in terms of writing.  It was delightful to be able to make things as complex as I wanted."

The Time Traveler's Wife is a genre-bender, a finely written literary love story with a science-fiction premise.  Artist Clare Abshire and punkish librarian Henry DeTamble are lifelong lovers, with a unique twist: their lives travel at different paces.  Clare's proceeds in the usual manner, day by day from youth to old age, while Henry, "a brand new kind of human," suffers from a rare genetic disorder that causes him to move at random through time.  Niffenegger uses this striking device in myriad ways, moving effortlessly from the rapturous to the grotesque.

The novel-in-progress went through many changes.  Niffenegger began with the title, and a fascination with themes of separation and waiting.  Though she started with an omniscient narrator, she quickly switched to Clare and Henry telling their own stories in short sections labeled like dramatic monologues, each with an accompanying date and the characters' ages.  "The essential unit was the scene, not the chapter.  It seemed entirely appropriate that it's fragmented, because that's how these characters experience their lives."

Early on, Niffenegger laid down her house rules for time travel, after reading a number of popular works on physics and genetics and consulting a science fiction writer's guide that outlines the genre's conventions.  "It was important to me that Henry would not be able to go back in time and change anything.  That can be fun, like Back to the Future, but then you're dealing with paradox.  I followed the physics principle of a block universe, that everything temporal exists simultaneously - you're moving through time as if through a house, so you experience events one by one, but they're all there at once.  Henry moves around in time almost as if it were spatial."

Niffenegger envisions Henry's disorder, which is eventually labeled Chrono-Displacement Syndrome, as a genetic mutation.  "Originally I thought of it as caused by radiation, kind of a Peter Parker/Spiderman thing.  Then I decided I didn't need to explain it - it's just modern life."

Henry's journeys through time are intensely personal, his sudden departures from the present often triggered by stress.  Unlike sci-fi time travelers who visit ancient civilizations at will, in peculiar machines, Henry travels involuntarily through his own life, arriving naked and clueless at certain key scenes in his future and past.  Sometimes he encounters an earlier self (one hilarious scene features teenage Henry in bed with a slightly older self, caught by his father in the act of literally playing with himself).  Sometimes he encounters a much younger Clare; she meets her husband-to-be when she is six and he is thirty-six, though when they meet in "real time," he's eight years her senior.  Young Clare remembers everything Henry tells her, though he's loath to reveal the immutable facts of the future, Sibyl-like, to those whose journey through time is more linear.

Henry's time traveling is fraught with danger - he's forced to learn criminal skills to clothe and take care of himself, and becomes a fanatical runner, training to save his own life when his journeys go bad.  He hides his condition from all but his nearest and dearest, struggling to live a normal life - not the easiest thing to pull off when you tend to disappear on short notice, and are often found wandering nude through your place of employment (his colleagues at Chicago's Newberry Library suspect some bizarre sexual kink).  But there are joys and reprieves as well, and a vision of meant-for-each-other, lifelong love that's breathtakingly romantic but never trite.

The book's construction is intricate.  Niffenegger worked with two different timelines, a linear one for Clare and a shifting one for Henry, to keep the hall-of-mirrors timeframe clear in her mind.  Her characters often surprised her.  "There's that cliché where novelists talk about their characters having an independent will.  I always thought that was idiotic, but I found it was true.  You have a very clear idea of who these people are, but that doesn't mean they always fit into what you want them to do."

The novel was carved out in odd slices of time around Niffenegger's day job as a professor in the MFA program at Columbia College Chicago Center for Book and Paper Arts.  The program has 37 graduate student majors, plus undergraduates and community members taking such courses as Bookbinding, Letterpress Printing, and Papermaking.  "These are former commercial processes that have been reclaimed by artists.  Otherwise, they might not have survived."

The process of making paper by hand is luxuriously detailed in The Time Traveler's Wife.  Clare is a papermaker and sculptor, but Niffenegger says her character's artwork bears little resemblance to her own.  "Clare works in 3-D, on a large scale.  Some of her work is kinetic, and all of it focuses on birds: their beauty and elegance, all the different metaphors that birds represent.  I work in two dimensions: books, photos and prints, and although I love beauty, I'm drawn to the strange."

Niffenegger and Clare share a number of superficial resemblances - they're both artists, born near Chicago, raised Catholic; Niffenegger dyed her hair red in homage to her character - but she feels that her personality is much more like Henry's.  "I have a sardonic worldview, a lot of skepticism, a dry sense of humor.  It was much easier to write Henry - his voice is my natural voice in the novel.  Clare is more sincere and serious, and far more patient than I am."

Niffenegger is currently staying at the Ragdale Colony in Lake Forest, Illinois, where she is "in theory" at work on her second novel, though she's still in the circling-around phase that often precedes hitting stride at an artists colony.

"This new one is amusing to me - I grew up reading 19th-century literature: Wilkie Collins, Dickens, Dorothy L. Sayers.  This is definitely a contemporary take on that style, but it takes place in London.  It's about a pair of young female American twins who inherit a flat near Highgate Cemetery, and wind up running into a lot of eccentric people."  Niffenegger had the concept for the new novel nearly two years ago, before the runaway success of The Time Traveler's Wife blew through her life like a hurricane.  Now she's come back to it fresh, and though she knows her characters intimately, creating their world is elusive.  "I'm on page 38," she sighs.

Ever the maverick, the best-selling author has chosen to write her new book without a contract or deadline, so that it can grow at its natural pace.  Still, there's comfort in knowing she won't have to send this manuscript to more than 20 agents, as she did with her first, and that thousands of readers are eager to see what she'll come up with next.  "There's a vast readership out there that's very agile and flexible.  There's such a long history of the novel now, and people who read, read quite a bit.  They're willing to go with new structures."  Niffenegger pauses, a smile in her voice.  "At least I am."  Judging from the enthusiastic fans of The Time Traveler's Wife, she's far from alone.