What the hell did I just read

Dave, John and Amy recount what seems like a fairly straightforward tale of a shape-shifting creature from another dimension that is stealing children and brainwashing their parents, but it eventually becomes clear that someone is lying, and that someone is the narrators. The novel you're reading is a cover-up, and the 'true' story reveals itself in the cracks of their hilariously convoluted, and sometimes contradictory, narrative.