There Are No Giant Crabs in This Novel

A heap of severed human limbs turns up in the parking lot of an abandoned department store, with bare footprints leading away from it. Nobody has been reported missing, and the fingerprints make no sense: some belong to living people who still have all their limbs, some match nobody on record, and some are missing entirely. It is, in other words, a case for John, David and Amy. The fifth book in the John Dies at the End series.