Dave's spellbook is the spellbook of Evil Dave. It contains handwritten spells, such as Teleport spells to the Makeover Mage, Grand Exchange, and Edgeville (all of which are actually the spell name written backwards), an inferior version of the Low Level Alchemy spell, and a spell of doom. It is locked by a magical phrase, hidden behind the boiler in the Basement of Doom.
When attempting to cast the spell of doom, an adventurer got some words of the spell incorrect, due to Dave's messy handwriting. As a result, they ended up swapping bodies. Dave then ran off, leaving the adventurer to try and sort out the mess while carrying out Dave's chores as punishment for repeatedly disobeying Doris. After managing to get Dave back to Edgeville, the adventurer attempted to recreate the spell using hell-rats, only for Doris and Dave to walk in, interrupting the spell. The adventurer was returned to their body while Dave and Doris had their bodies switched.