This book is clearly written and well-edited, with a wealth of usable information presented in a way that is easy to find. I've been reading online books about LATEX and have bought other books from Amazon, and created a few (very few) documents with them. This, though, enabled me to go back and re-edit what I'd done, make it come out better, and, in a few asides, suggested new possibilities for using the /date function to create subject lines in a letter.
Even if you've already read something else, take a moment and go through this book. It's worth the price and the time: not something I can always say.