I finished Linchpin a few weeks back and that was an amazing book
Will It Fly is a great book I learning a lot of great marketing tricks from
I have to say, I learned a ton of cool tricks that one would have to spend weeks reading through forums to learn.
The part on how to build a market map is worth its weight in gold.
I opted for the kindle book, and the audio add on was only $2 which is an amazing price if you have bought other audio add ons.