Hello, I just bought Asterisk: The Definitive Guide 4th Edition at Amazon. The book will be released on May 28 (or so I believe) but right now Amazon is selling it at Pre-order price. I bought a copy yesterday for only $29.99. The book will cost $54.99 so if you are planning on getting it you should buy it now. I have read previous versions and think it is the best Asterisk book. So far I've only used Asterisk 1.6 and 1.8 and this book covers Asterisk 11 so I will update my knowledge about Asterisk to the most recent version.