You want thorough? Try 298 pages on a show that’s barely two seasons old. Golden and Holder’s official guide to The WB’s ghoulish teen drama (not to be confused with “The Girl’s Got Bite,” an upcoming unauthorized companion to the series) covers everything from character sketches to cast bios to where costume designer Cynthia Bergstrom shops for Buffy and her undead-hunting pals. Since the beauty of “Buffy” is its stake-sharp writing, the authors rely heavily on excerpted dialogue to explain the series’ vampire lore and the coffin-crossed love story between hunky vampire Angel and the Slayer. Sure, it’s excessive (do we really need bios of one-time guest stars?), but addicts will no doubt suck this trivia-laden tome dry with fanatic ferocity.