I loved this book. The first third of it is autobiographical - King's childhood, and how he began writing, up to the point where he started making serious money from it (and his description of hearing that the paperback rights for 'Carrie' went for $400,000 is very funny: "The strength ran out of my legs. I didn't fall, exactly, but I kind of whooshed down to a sitting position..."). Then there's the meat of the book - his thoughts on writing (how to, where to, how much to and a great deal more besides). Then there's a whole list of post scripts, of various kinds. It sounds like a dog's dinner, but it's all hugely readable, and as relaxed as if you were just sitting in a bar with King and he was simply talking.
Yes, it's aggressively opinionated, it's all about him, and I'm not sure why being a best-selling author necessarily entitles King to instruct others on how to write. Much of the advice is trite: avoid adverbs and the passive voice is very much 'How to write 101'. He's totally scathing about some techniques beginning writers use (like creative writing workshops), and insistent that his own ways work best - have your own space for writing, write a set amount each day no matter what, write with the door closed, edit with it open. Well, I can imagine lots of aspiring writers sighing at this, and saying: "It's OK for you, mate - chance'd be a fine thing".
But it's funny, and I can forgive a book almost anything if it makes me laugh out loud. It's sharp too - of creative writing seminars, he says: "It is, after all, the dab of grit that seeps into an oyster's shell that makes the pearl, not pearl-making seminars with other oysters." And it's very down to earth - when he talks about editing, he shows you a few pages of a first draft, and then the same pages with his changes scrawled all over them, and he tells you exactly why he made every single change. So there is a certain amount of useful advice in there, although wrapped up in an awful lot of rambling (if amusing) Stephen King reminiscence.
So if you can accept the book for what it is - a very entertaining autobiographical piece, with a few nuggets of writing guidance - rather than a handbook to set beginning writers on the path to fame, fortune or the Booker prize, it's a fun and enjoyable read, from start to finish. And his bottom line is a gem - anyone who wants to be a writer should read a lot and write a lot. You can't fault that.