Here’s two books which I definitely recommend:

Call to Action: Secret Formulas to Improve Online Results
Somehow Call to Action escaped my reading list for years. I learned about it from someone I recently interviewed. The book is based on Bryan and Jeffrey Eisenberg’s concept of Persuasion Architecture—a methodology which, at a high level, combines consumer psychology, business goals and website design with an overall goal of maximizing conversions.

Web Analytics: An Hour a Day
I’m one of those people who can’t get enough of web analytics. Written by respected blogger and Google Evangelist Avinash Kaushik, this book demystifies web analytics in an easy to read, enjoyable manner. The practice of web analytics isn’t as simple as it may appear at a glance. Avinash’s book provides new perspectives in a concise manner.