Josh Kaufman's 'Your Personal MBA' is excellent - its rare that you have one book which goes through all of targeting, segmentation, positioning, marketing planning, and how it all sits together. Often books will focus on one small piece (like positioning, or value propositions) but without understanding how these pieces sit into the wider whole it's hard to put them to really effective use.

Byron Sharp's How Brands Grow is also a great book from one of the world's leading marketing professors, and aims to lay out some iron laws about buying behaviour. Byron is quite a spiky and contrarian personality, which makes the book a lot of fun to read, but he also really knows his stuff.