I would like to recommend this SDR book. It is technical and
mathematical but well done by an acquaintance of mine at the Univ. of
Utah.
http://www.ece.utah.edu/~farhang/
You may follow his link to lulu and for $13.00, download a pdf version
of his book. He is an extremely bright professor at Utah. His college
team did very well in the SDR Forum challenge in 2007.
Bob