This is an excellent book for the basics. As a non-mathematician, it was really useful to me. With its many figures and explanations it helps to understand the equations and doesn't just give them and proof them as many books in this field do. Its chapters about Fourier transform, averaging, Laplace and z-Transform and digital filters are really well written. Also this book will help the average human being to understand wavelet transforms. The only drawback of the book is that it covers really just the basics. You might have a problem of which you think that it's simple but the book might still not cover it. This is for example true for the Hilbert transform.