The Triathlete's Training Bible by Joe Friel

Garbage is probably a bit harsh, but I understand the sentiment. The book is thorough and based on sports science as far as I can tell. I'm surprised at the 'garbage' comment made earlier in this thread - mainly bc no reasons to support the charge. You will find somewhat conflicting opinions between these books and if you follow each book's steps to create your own training plan, you will end up with three fairly different plans. Two other books I would recommend are Triathlete's Guide to Training with Power by Philip Skiba and The Well Built Triathlete by Matt Dixon. There are (surprise!) different opinions on how one should train for triathlon. I'd you're really interested training theory, I probably wouldn't stop with the Triathlete's Training Bible. You can skip around and hit the necessary chapters to get a rough plan going in not much time. It covers all the basics and doesn't assume too much prior knowledge. It is a great book overall, and a great first book to read if you want to be knowledgeable enough to plan your own training without the help of a coach. If your budget is really low, the 3rd edition is fine and contains 90-95% of the same content.

It has some new and changed content that is more in line with what seems to be the current consensus, specifically around training periodization for preparing for long course races. I have the 3rd edition and borrowed the 4th edition and read most of it.

The Triathlete's Training Bible by Joe Friel