WordPress Mobile Web Development Beginners Guide book is published by Packt Publishing and written by Rachel McCollin. Book contains a lot of information on plugins and themes you need for website, setting up mobile specific media queries, layouts and more.
WordPress Plugin Development Cookbook book is published by Packt Publishing and written by Yannick Lefebvre. Book contains 80 practical step-by-step problems with easy to follow solutions to most common problems developer can have when creating plugin for WordPress.
It’s no secret: I don’t like how WordPress development is handled over the past year or so. And best thing I can say about WP 3.4: it is a big maintenance release; all important changes are mostly tweaks or API related. My favorite features are Twitter embed and toolbar click top scroll.