Grok book published
http://www.packtpub.com/grok-1-0-web-development/book
The book is intended for developers more or less familiar with the concepts of web applications who want to write their applications using the Python programming language. No familiarity with Zope is assumed from the start. The approach is practical, focusing on getting working code right from the beginning.
The foreword is by Philipp von Weitershausen, Author of Web component Development with Zope 3 and an early Grok contributor. He made a blog post out of it, which can be read at his site.