An oddity--a comic rime-travel novel--but no odder than DiSilvestro's comic werewolf novel, Ursula's Gift (1988). And not much better: this former Audubon magazine editor seems to shine only at straight nature writing (Audubon Perspectives: Fight for Survival, p. 624). True, DiSilvestro has dropped most of the racist and sexist humor that made Ursula's Gift so offensive (although he still has trouble with women; of the three featured here, two get their heads chopped off and the third has hers shrunk, Amazon-style) What he hasn't got rid of are dÃ‰jÃ¡ vu characters and plot--beginning with hero Jackson Black, who's hired for his photographic memory by a crippled billionaire, Mr. Ritz, to help find a UFO that's crashed in the Amazon jungle. Mr. Ritz hopes the UFOnauts can cure his paralysis--except that that wasn't a UFO at all, but a ""chronocraft"" piloted by ""Time Police"" chasing a second chronocraft flown by sub-hero Tyler Blake, here from the pollution-blighted 21st century to find a cure for a future plague. Mr. Ritz confiscates the intact chronocraft, but then flies it into the past and meets his younger, healthier self, who shoots him dead. Meanwhile, Black and Blake link up with a time cop, Hunter Rodale, who flies them into the future--only to find a pristine world, devoid of humanity. Seems that the younger Mr. Ritz has gone back to the Middle Ages and altered history by conquering the world and killing off all people except for a few slaves. To undo Mr. Ritz's work, Black & Co. travel to 878 for an adventure that sees them fight knights, outwit Vikings, counsel Alfred the Great, beat Mr. Ritz, romance and behead women, and generally have a bloody good time of it. And being a conservation-minded sort, Black even figures out a way to recycle a woman after she's lost her head. A tired ersatz-sf parody, told with large doses of eco-morality but little style, originality, or wit.