When O'Reilly promoted their cyber monday I somehow really got into a shopping spree.

First book I finished now is Code Simplicity by Max Kanat Alexander. The book doesn't hold on to the scientific approach that the blurb promises but once I made my peace with that it became a good read.
Some of the things I liked most:

• It provides good reasoning why an iterative process usually provides better results than the old Plan & Implement workflow.
• It has a strong argumentation for testing that can help you the next time you have to explain why it is important or understand it yourself if you didn't so far.
• It gives you some great new angles on how to prioritize features.

Overall I'd probably recommend the book but you shouldn't expect to much scientific proof. Probably that's not even possible in that area but the blurb said so and that caused some bad reviews so take it with a grain of salt.

You can find all of my personal highlights on Readmill