I found the Pro BizTalk 2006 book really good and now since Microsoft have released the BizTalk 2009 version I was thinking that new books should come pretty soon.
And here it is. The Pro BizTalk 2009 will be soon in the market. Its by authors George Dunphy, Harold Campos, Stephen Kaufman, Peter Kelcey, Sergie Moukhnitishi, Davi Peterson.
Also the Book Pro Mapping in BizTalk 2009 looks good at first glance. I am reading that and I ll post hows that. The Pro Mapping is from Jim Dawson and John Wainwright.
Some how I like all the Pro's by APress. Even the Wrox ones are good. I have a account in http://skillport.books24x7.com which is online books database and almost all the new released BizTalk books are there. Once I am done with the Pro Mapping one I will be reading the Pro BAM in BizTalk Server 2009 by Jeff Sanders and Geoff Snowman.
Till than Happy BizTalking....!!!!!!!!!!!!!!!