I'd like to find more resources / books (I love audio books these days) that answer some of the questions at the bottom of Marc Andreesen's original post: - Ho

I'd like to find more resources / books (I love audio books these days) that answer some of the questions at the bottom of Marc Andreesen's original post: - How exactly do you go about getting to product/market fit if you don't hit it right out of the gate - How do you know when to change strategy and go after a different market or build a different product? Anyone have books on some of these mechanics?