The author was an English major in college, which must be why the book was so easy to read. The first part of the book is primarily historical in nature, explaining how wavelets (as of 1998) came about. In this part will be boxes with some technical details. The second half of the book has chapters for each of these boxes explaining the theory in more detail.
Note that I believe (and follow) the meanings Goodreads gives for what each number of stars means. Therefore, the majority of my ratings are 3 stars ("liked it").