I have this book and use it all the time. Your five star rating is right on the mark.
I only have one bone to pick. There is an error that is repeated in example code throughout the book. The sacred-to-sort package globals $a and $b are used as generic temporary lexicals. That's harmless in the examples, but it's bad practice, and it might lead to grief for a reader experimenting with the code.
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>