This is a small compact reference book (hence the title) which lists the HTML tags in alphabetical order, shows if they are supported by the three major browsers (IE,NN,Opera) and if they are part of the w3c spec HTML 4.01. Information is given for the applicable attributes for each tag.
Once you know it (especially if you follow w3c standards) HTML is a simple and easy language to use.. however, having a easy to use reference comes in handy quite frequently, especially when starting up a new site.
This will not be the only reference you need.. no book can claim that. Though everybody who designs websites should have this book, those new to HTML may find it the most helpful most frequently. However, this book will NOT teach you HTML. It is a reference.. nothing more.
as mentioned in other reviews.. the IMG tag is missing, which is a major flaw, but not major enough to take away from the greatness of this book.
In short.. get it.