The Woods Out Back by R. A. Salvatore

Napping after a dreary day in his dead-end job, Gary Leger wakes to find he has been kidnapped into "the world of the Faerie." Mickey McMickey, a leprechaun, has brought him to join the quest of Kelsey Gil-Ravadry, an elf who hopes that by following "the legends" he can repair a spear that belonged to an ancient king; the spear has great powers and is able to communicate with its possessor. Gary's reluctance to go questing is overcome by Kelsey's simple argument: help me or I'll kill you. As the trio ventures forth to corral a dwarf blacksmith (to reforge the spear) and a dragon (to supply the fire needed), they find themselves thwarted by the evil sorceress Ceridwen, who sends trolls and goblins to attack them, among other impediments.