Thanks for your question!
This time I thought I'd hand it over to one of my UX buddies at Optimal Workshop to answer. So here's Matt with a couple of great recommendations.
The books Matt refers to in this video are:
- Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics by Tom Tullis an Bill Albert
- Quantifying the User Experience: Practical Statistics for User Research by Jeff Sauro and James R. Lewis