This book contains some wrong and oversimplified statements, the explanation of the sampling theorem is awkward and suggests that the author has not fully understood it himself.

Example of wrong claims: "The heart of digital noise generation is the random number generator." Not true, many digital noise generators use LFSR.

"Just as analog filters are designed using the Laplace transform, recursive digital filters are developed with a parallel technique called the z-transform." Hello no, there are gazillion ways to design filters - analog or digital - without those transforms.

"The frequency domain becomes attractive whenever the complexity of the Fourier Transform is less than the complexity of the convolution. This isn't a matter of which you like better; it is a matter of which you hate less."

Clearly I hate both domains less than this book. It might serve as an introduction to DSP, but please remain suspicious, if some claim herein seems oversimplified, it probably is.