The journal of Joseph Mason, thirteen, records his adventures as the assistant of one Mr. Audubon, a painter with a ""regular passion for birds,"" on a flatboat trip down the Mississippi. Joseph soon learns that his master, flat broke, intends to pay for the passage by providing game for the boatmen; therefore hunting, and even cooking detail for Joseph, are added to long sessions of drawing, in which Joseph specializes in adding the botanical backgrounds. Mr. Audubon, a gentleman except during his depressions, turns out to be extraordinarily accident-prone--one folio is lost, another nearly ruined when gunpowder explodes inside his luggage. And Joseph puzzles over contradictions in his mentor's character: Audubon regrets having to kill so many birds for the sake of his painting, yet risks poisoning his favorite dog, merely in order to disprove an old wives' tale about parakeets' hearts being poisonous. Yet it is their shared enthusiasm for art and rare moments such as a day spent watching eagles in their nesting ground, that cement Joseph's deep admiration; not even his discovery eighteen years later that his name has been removed from the paintings can destroy Joseph's respect for his teacher's genius. Joseph Mason really existed; his journal, recreated from references in Audubon's own diary and other biographical sources, has more heart and less artifice than other such constructions. One hopes that Brenner's subdued tone--and the dark, low-contrast look of the black-and-white period reproductions, including six Audubon prints--aren't such a low-keyed combination that Joseph's sturdier virtues will be overlooked.