I tend to get emails from folks asking if there are any good books out there on "Subject X".
I did find a good one for Exchange Server 2007 that has been updated for SP1 and is written by an MVP out of Washington. William R. Stanek is the author of the Exchange Server 2007 Administrator's Pocket Consultant 2nd Edition published by MS Press in May of 2008.
You can find it on Amazon or Barnes and Noble - links are below.
If you are interested in other books that William R. Stanek has written, feel free to visit his website: http://www.williamstanek.com/