Last time around the Real World SharePoint 2007 book was one of WROX's most successful SharePoint books. Well, here we go again! The 2010 version that I was involved in is now available on Amazon for ordering today!
My chapter is on building custom service applications but I don't cover just HOW to create them. The important thing that most people don't understand is WHEN to create them. I've talked to some folks who say that's all they are building... hmmm... not so sure they've got it right as very few people should be building these in my eyes. They are quite involved and you need to ensure you are doing it under the right circumstances.
It's also available in Kindle format as well!