Victims (Alex Delaware #27) by Jonathan Kellerman

Not since Jack the Ripper terrorized the London slums has there been such a gruesome crime scene. By all accounts, acid-tongued Vita Berlin hadn’t a friend in the world, but whom did she cross so badly as to end up arranged in such a grotesque tableau? One look at her apartment–turned–charnel house prompts hard-bitten LAPD detective Milo Sturgis to summon his go-to expert in hunting homicidal maniacs, Alex Delaware.

But despite his finely honed skills, even Alex is stymied when more slayings occur in the same ghastly fashion . . . yet with no apparent connection among the victims. And the only clue left behind—a blank page bearing a question mark—seems to be both a menacing taunt and a cry for help from a killer baffled by his own lethal urges.