Packt Publishing have a new book on WordPress theme design:
“This book walks through clear, step-by-step instructions to build a custom theme for the WordPress open-source blog engine.
The author provides design tips and suggestions and covers setting up your WordPress sandbox, and reviews the best practices from setting up your theme’s template structure, through coding markup, testing, and debugging, to taking it live.
The last three chapters cover additional tips, tricks, and various cookbook recipes for adding popular site enhancements to your WordPress theme designs using 3rd-party plugins as well as creating API hooks to add your own custom plugins.
Whether you’re working with a pre-existing theme or creating a new one from the ground up, WordPress Theme Design will give you the know-how to effectively understand how themes work within the WordPress blog system enabling you to have full control over your site’s design and branding.”