The idea is a good one, and under Barker's name it has the potential to fulfill its promise. But Mister B. Gone would have been better as one of Barker's short stories, which tend to be light and frothy, and make up in wit and verve what they lack in outright horror. Mister B. Gone's narrator, Jakabok Botch, has a bantering tone, and his adventures in medieval harrowing are related with an insouciant charm that could have made the acts he commits seem truly gruesome.
Instead, for the length of the novel, Botch cajoles the reader directly. He makes promises and threats. He even begins addressing the reader as "my friend" around page 43, giving the rest of the book the desperate ring of a public radio pledge drive. Meanwhile, words are repeated from paragraph to paragraph. Seemingly, Barker couldn't think of a way to describe old trees other than with the phrase "immense girth." It's as though he ran through one draft and dashed Mister B. Gone off to his editor while he sat down to lunch.
Much of Mister B. Gone's short page count is spent asking/convincing/boring the reader to burn the book itself, which seems like an attempt to make it seem important. Having finished the novel, I'll spare you any suspense the cheap theatrics might cause: It's not worth it. No Mister Barker, I'll not burn your book. I'm going to do the modern equivalent though, and send it to the "Used" bin at my local bookstore. At least they'll give me some store credit for the story, which is more than you deserve.