Since H.G. Wells' landmark ''The Time Machine,'' depictions of temporal journeys tend to be an amalgam of science and fantasy. ''Wife,'' however, is a love story in which time travel plays a supporting role. Here, librarian Henry suffers from a genetic condition that unpredictably flings him through the past and future, and his jaunts fuel his lifelong relationship with artist wife Clare. (A sexy premise indeed: Film rights have already been snapped up by New Line with Brad Pitt attached to produce and star.) The comparison of wistful Clare to Penelope, patiently awaiting the return of her Odysseus, may be a stretch -- a timeless romance this is not. Still, Niffenegger's inventive and poignant outing is well worth a trip.