If you are forced to do SharePoint development and you only have time for one book, this is the book for you. Very clear, relevant examples, and well-written. I have returned to this book time and time again for the information that Microsoft's documentation fails to provide.
This is a very good book for anyone wishing to develop for SharePoint. It's a must-have for any developer because of its in-depth knowledge of various quirks of the platform that aren't readily available in the MSDN.