A good under-the-hood SharePoint book?

My former colleague Kjell-Sverre has written a review on the book Building the SharePoint User Experience, where he absolutely recommends reading the book. This is a hardcore book for SharePoint developers. I haven’t read it yet, but it’s on its way.

Kjell-Sverre’s review is worth reading, including his follow up post on List Content Type Forms

Building the SharePoint User Experience (Expert's Voice in Sharepoint)