For me, the most interesting part was the auto-biographical half. Stephen King has a kind of 'rags to riches' story and, of course, he made his riches by becoming a successful writer. This is very inspiring to someone like me, who's a poor, so far unsuccessful writer! I'm sure any people who write will be able to appreciate it for the same reasons as me. He also talks about a serious car accident his was involved with and how that affected his writing output too, which was a good read (even if a little sad).
The half of it which was actually geared towards helping you to become a better writer, while good, didn't interest me as much. As somebody's who's done a three year long Creative Writing course I've received a lot of advice on how to improve as a writer; Stephen King's advice isn't all that much different to what I had heard before, but I guess it's important to refamiliarise yourself with those sorts of things. Plus, if you've never taken any Creative Writing classes this stuff will probably all be new to you and therefore very useful and important information!
Overall, this is definitely a book I'd recommend. The autobiographical segments mean that you'll be able to enjoy the book even if you don't plan on becoming a professional writer and, who knows? Maybe you'll read Stephen King and be so inspired by his story that you decide to take up writing yourself! Rating: 8.7/10