Though best known for his occult horror (Midnight Sun, 1990, etc.), Campbell built his career on psychothrillers barely tinged with the uncanny (The Doll Who Ate His Mother, 1976, etc.). Here's a new one, about an antic serial killer, intriguing for its unusual blend of horror and farce but lacking much punch. Jack Orchard, owner of a suburban Liverpool video-store, believes wholeheartedly in luck--which he's fresh out of: As the story opens, a series of pratfalls causes his shop to burn down; he's denied a bank loan; and he learns that his shop was uninsured. But then a chain letter arrives, promising to ``turn ill luck into good'' if Jack mails it to 13 others, which he does. And it seems as if his luck is changing--until a hoped-for job falls through and his daughter is attacked by thugs. To Jack's increasingly addled, numerology-clogged mind, this can mean only that some recipients of his letter failed to mail it on in turn, with misfortune rebounding on ``whoever's most accident-prone''--i.e., Jack. What to do? Why, confront the culprits and--for reasons Campbell never quite makes clear--begin to kill them off with a blowtorch. The first murder does seem to improve Jack's fortune--he lands a job--but when his wife loses hers, it's time for several more deaths, most depicted in gruesome slapstick (``a convulsion of his whole body sent Foster jackknifing backward several feet. `Murder,' he shrieked, `murgle, murglub,' and sank''), until Jack becomes known as the ``Mersey Burner''--and then slips off to Greece, where he ends his spree. There's no doubt a gleam in Campbell's eye as he confounds thriller conventions--no cop-vs.-killer here, and little suspense- -and lays on the wryness, but, despite lively language and character-shading, Jack's evolution into a killer doesn't wash, the murders become repetitive, and the ending lies flat on the page. Back to the occult, Mr. Campbell, please.