A book about extension development for TYPO3 CMS with Extbase and Fluid has been released in English.
There hasn't been much published recently in English for TYPO3 so this comes as a delightful surprise.
It should be a good guide for somebody wanting to use the Extbase framework and the Fluid templating engine to make their own TYPO3 extensions.
The book description page says this book "provides all you need to know to get up and running with Extbase and Fluid in an easy-to-follow format with real-world examples."
Oh, and you can buy the book, of course, through many different channels.