"When I feel like being a director," John Irving confesses in his slight but engaging new memoir, My Movie Business, "I write a novel." This piece of hard wisdom arrives at the end of Irving's 13-year struggle (with four different directors) to adapt The Cider House Rules for the screen, a process that would inevitably leave the finished product out of his hands. But the book's surpriseand, to a certain extent, its disappointmentis that on the whole, Irving seems perfectly happy with his experiences in Hollywood, making all his time, revisions, and minor compromises worthwhile. Far from the acrimony that usually results from a great author's horrific encounters with the studio system, My Movie Business is a mild and insightful reflection on the genesis of The Cider House Rules and its resistance to adaptation, with a few chapters on previous collaborations squeezed in. Rushed to print in order to coincide with the film's release, its exhaustive history of every cut and addition to the story will only be useful to those who have read the book and/or seen director Lasse Hallstrom's polished, sensitive rendition. Irving admits that Cider House "is a didactic novel," and it's precisely this didacticism that he fights for as a screenwriter. Inspired by his grandfather, a Boston pioneer in obstetrics and gynecology, he wanted the goings-on at a mountainside orphanage in Mainewhere pregnant women always leave without their babiesto serve primarily as a passionate argument for abortion rights. To Irving's immense satisfaction, the like-minded Hallstrom strikes a good balance between the hot-button social issue and a more conventional love story. (No points for guessing which angle the film's distributor, Miramax, is emphasizing.) For all its merits, My Movie Business leaves a couple of obvious questions unanswered. Why does Irving spend pages praising the screen versions of The World According To Garp and (gulp) Hotel New Hampshire while failing to mention Simon Birch, which so badly mangled A Prayer For Owen Meany that Irving went to unusual lengths to distance himself from the wreckage? And why was it so important for him to spend the time and energy it took to bring The Cider House Rules to the screen? After an "odyssey" lasting more than a decade, writing countless drafts for separate directors, Irving's contentment remains both admirable and deeply puzzling.