I highly recommend anyone working with MySQL in any capacity to pick up a copy of MySQL: The Complete Reference; it's the most thorough, easy to follow, well laid out book on the subject I've seen (and I have several computer texts, many of which deal with MySQL in some way or other). Every facet of MySQL is covered: system admin, table types and structure, data types, basic to advanced SQL syntax. There are sections dealing with new features in v4.1 (still considered under development as of this writing) such as subqueries (which are going to be a huge help) and other new methods for handling data. My favorite parts of the book are the nested sidebars that have tricks and tips for doing things in one of several different ways, most of which I've never seen before.
The most impressive feature of the book, in my opinion, is the balance between visual examples and technical detail. Usually you find a computer text is strong in one or the other; the author Vikram Vaswani has done an excellent job in illustrating his talent to show the end user exactly what he / she needs to see to understand the task at hand, not to mention his depth of knowledge on the subject. The book has MySQL's logo on it for a reason, people.
I had personally put off purchasing a book on MySQL, instead relying on online documentation and tutorials. When I realized I wasn't moving in the right direction, I took a look at several available texts and chose this one. Even though I've been working with MySQL for over a year, after having read a majority of the book, I can honestly say I've easily doubled my understanding of syntax and the inner workings of MySQL in the past two weeks. Less than half an hour after reading the chapter on JOINS, I was able to construct a complex combination of self and left join that had been eluding me. I'm currently going through several tables and scripts, optimising table structure and syntax based on lessons learned. I only wish I bought two copies, as mine is already dogeared and worn from taking the trip back and forth from home to the office every day!
If you only take one thing away from this review, let it be this: you WILL learn MySQL from this book!!