Are you looking for something on acoustics? OR just speaker placement? Or HT in general? There are several good books on amazon about HT if you search for "Home theater", and the master handbook of acoustics is a good general acoustics book. You can do a lot with speaker placement by trial and error too(doesn't cost anything but time), though the room acoustics is important.
The Dolby Guide to Home Theater Sound Also contains a great deal of useful info on room setup. Note that this is just a guide and does not have to be followed for a enjoyable HT if your room or decor does not permit.
One of the best sites available for such matters is www.dolbydigital.com. They have pretty a pretty good FAQ area that defines a whole lot as well as a good knowlegebase.