''The only person who sees dead people is Haley Joely Osmond, or whatever his name is,'' Mark Underhill's best friend tells him, but that doesn't stop 15-year-old Mark from poking around a spooky abandoned building in search of spirits who might explain his mother's suicide. Straub's first novel since ''Black House,'' his brilliant 2001 collaboration with Stephen King, freshens shopworn horror elements -- an undead young girl, a haunted house, a serial killer -- with an inventive structure (incorporating e-mails and journal entries), masterfully fleshed-out characters, and real emotional content. As a result, ''lost boy lost girl'' proves much more than just a ghost story: Straub puts the natural back in supernatural.

