Getting Started with Magento Extension Development

This is a really good book. I would recommend it to those who would like to start with basics.

An excellent book for Magento developers, written by the CTO of Inchoo (inchoo.net), Branko Ajzele. IMHO, this book and the new 'Magento PHP Developer's Guide', from the same publisher... are the best reading about Magento development.The book begins with an overview of the Magento structure, from the directory level to the module level. It guides reader through several building examples of extensions, involving critical areas, and real-world techniques like:- Using event/observer patterns.- Using Models with installation/uninstallation scripts.- Usage of datagrid in the administration backed.- Developing your own payment method extension.- Processing and packaging the extension for distribution over Magento Connect marketplace.