Part Biography and part review of King's literary and film works (up to the mid 80s at least), this book was very interesting. The author is an avowed King fan, so it is not a surprise that he praises everything King wrote up to that point (of course, all that stuff was awesome, so I can't fault the author for that).
I learned a few things from the book, including the fact that the Dark Tower series was expected to be released as a large collection of short stories (The Gunslinger is a collection of 5 related short stories, though now we just consider them all one book). There are several references to The Cannibals, including its original title "Under the Dome," which it eventually retook when it was published recently. I found the most interesting aspect of the book was finding out when King wrote everything (books weren't necessarily written in published order and some of the story collections were written over many many years).
I'd like to read an updated version of this book, bringing in all the work he's done over the 25 years since this book came out.