Stephen King's On Writing. It gave some background information about him, where he came from and what he worked through, and also throws in his suggestions with what's worked for him in the realm of writing. I thought it was well-done, interesting, and had some good advice. I didn't get bored and I didn't believe that he was just spouting nonsense.
The only one that really helped me was Adele Ramet's Creative Writing - at least, I think that's what it's called. It helped me to develop character sheets for my novel (I only used them for my first ever novel, and I've only used them loosely and vaguely since). You might find it useful, or even an interesting read, depending on how much you like to read books on writing and how developed you are as a writer.
I'm reading Sol Stein On Writing at the moment. The guy is a friggin genius is you ask me! I have learned so much from reading just a few chapters. Now just to apply this to my own writing (well that's another story) lol
