Baumbach, an erratic, sometimes experimental writer, is usually most engaging when--as here--dealing with father/son tensions. And the son this time is Tom Terman, 18, who jets to London to visit his novelist father, Lukas. Years ago, Lukas had abandoned the family; in England, he's been engaged for years in writing a movie script, a thriller, whose production is always being postponed by director Max Kirstner. And Isabelle, a model with whom Lukas has a semi-attached relationship, moves out of the house before Tom arrives. But the discretion is unnecessary, since Tom stays with his father merely a day, moving out afterwards to a boardinghouse instead (and taking with him a pistol he found in one of his father's desk drawers). Throughout, in fact, behavior here is never quite what it seems: Tom's not sure what he's doing in London, with a father he probably doesn't like; Lukas finds the visit baffling as well; the father-son tension is echoed by the neverending-ness of the movie project, the making-up of scenarios which have only the most tenuous grip on what's real. And there's always that gun Tom has taken: Will he kill Lukas with it? Kill himself? Do nothing but carry it about? Thus, though the narrative becomes cloudy at regular intervals, Baumbach has fashioned an entire book out of not-quite-assignable tensions, somewhat in the style of British novelist Nicholas Mosley. Mirrors and movies, stories within stories: these are all commonplaces of a certain serious kind of funhouse fiction, but Baumbach here uses them elegantly and vaguely enough to present a slippery tale that's as intriguing as it is elusive.