The Murdstone trilogy

"When yound adult author Philip Murdstone's star starts to wane, his agent, the ruthless Minerva Cinch, convinces him that his only hope is to write a sword-and-sorcery blockbuster. Unfortunately, Philip is utterly unsuited to the task. In a dark hour, a dwarfish stranger comes to his rescue. But the deal he makes with Pocket Wellfair turns out to have Faustian consequences."--Provided by OCLC.