Fourier and Wavelet Signal Processing has evolved into a pair of books:

• Signal Processing: Foundations
• Signal Processing: Fourier and Wavelet Representations

Together, these books aim to present the essential principles in signal processing along with mathematical tools and algorithms for signal representation.  They comprehensively cover both classical Fourier techniques and newer basis constructions from filter banks and multiresolution analysis—wavelets.  Furthermore, they gives a synthetic view from basic mathematical principles, to construction of bases, all the way to concrete applications.

Current free versions:

• SP:F (beta 1.0 release) (8.8 MB, 22 Mar 2012)
• SP:FWR (alpha 3.1 release) (5.9 MB, 22 Mar 2012)