Upon first glance it might seem that Jennifer Crusie, a prolific romance novelist whose credits include such titles as Faking It (2002) and Man Hunting (2001), would have little in common with former Green Beret and thriller writer Bob Mayer. But that didn't stop the pair from joining forces on the job: they recently co-authored Don't Look Down (St. Martin's).

These two aren't alone, either—a spate of authors have teamed up to try their hands at his and her love stories. Later this month, Algonquin will release an epistolary novel, Which Brings Me to You by Julianna Baggott and Steve Almond, about a clandestine tryst at a wedding that develops into a love affair through letters. And in May, Knopf will hit the market with a YA title by Rachel Cohn and David Levithan, Nick and Norah's Infinite Playlist, which follows the development of a relationship between two lovelorn teenagers after their impromptu meeting in Manhattan.

So why the sudden boom in the he said/she said approach to the love story? It seems to be something that's striking many of these writers as an enjoyable experiment. According to Jennifer Enderlin, who edited Don't Look Down, the idea for the book came out of a chance meeting between the authors at a writer's conference. Crusie, who was suffering from a bit of writer's block at the time, began corresponding with Mayer after he suggested they work on something together. The fruit of their labor has turned into a 115,000-copy print run and a 25-city tour.

Enderlin also thinks there may be certain advantages to having two authors. Not only does St. Martin's hope each author will bring their respective fan bases to the book, the two are also now on board for a second collaboration. The dual byline may also pique interest. "People are curious to see what a Green Beret would be doing with a romance author," Enderlin said.

Nick and Norah also began on something of a whim. The two seasoned YA novelists tossed the idea around over lunch and then, when Levithan e-mailed Cohn out of the blue with a first chapter months later, the writing process officially began. Cohn started responding in the voice of Norah while Levithan started speaking as Nick. As Cohn writes in the foreword to the book, she was hooked immediately. "With one file attachment, my life was over. All I wanted to do was wait by my in-box to read Nick's latest installments—and respond as Norah." The book, which comes out on May 23, will have a first printing of 40,000.

Cathy Pories, who edited Which Brings Me to You at Algonquin, also admitted it is nice to be behind something that can pull from the followings of two authors. But Baggott and Almond—who were old friends from their days as M.F.A. students at UNC Greensboro—weren't interested in necessarily playing up the device, and neither was their editor. "Sure, it's an added way that the book can be pushed, but it was definitely never the motivating factor [for doing it]. I'm leery of gimmicky books." The title, which received an "A-" review from Entertainment Weekly, has a 20,000 first printing planned, and the authors are set for a seven-city book tour.