Well, Rob Foster, Murray Gordon, John Alexander, and Myself have all been working on competitive SharePoint 2007 books this past Fall/Winter and they are all being published around the same time. Personally I would suggest purchasing MINE first, but then definitely support the other guys.
Honestly, these guys are my friends and I communicate with them frequently so I hope their books sell well. Rob and I have vented to each other via IM about SharePoint when we ran into issues serveral times. Hopefully we will each trade a copy of our books when they are published.