if you want to know more graph theory than you can get from this book, you probably don't need me to tell you where to look. surprisingly readable, and it doesn't assume much prior knowledge. beats the crap out of bollobas.
I must admit that I really don't understand why this book is so highly rated. It is a good reference material. But as a learning material it's really horrible.
The definitions are way to obtuse (confusingly similar notation used for distinct things, at several places new terms are used without ever being defined) and terse for learning. Unless you have someone at hand who already understands the presented notions you will slog through the content very slowly.
Comprehensive textbook with challenging questions in each chapter. The short proofs leave a lot of gaps for the reader to fill in by herself; my professor described Diestel's proofs as being more like "sequences of claims" than proofs. This style, though, allows the book to pack information into reasonably sized chapters, stating concepts clearly instead of shrouding them in the minutia.
Too terse for my taste. The proofs are too telegraphic, probably with the intention of treating a large number of theorems / results. It's an excellent compendium (a lot of new material) but it's not a book to learn Graph Theory from.
I read this book outside of a course, without any pressures, because I'm interested in Systems Science (which often uses Graph Theory). I've also never read a GTM book before, so though I'd see what it was like.
The writing is clear. Each chapter is well introduced, the notes at the end are very helpful, being separate means that they don't interfere with the reasoning, but the background rounds out the material very well. The progression from one chapter to the next is clear and made sense to me. The marginalia referring to other theorems, lemma, and conjectures is very helpful. The index and list of characters was also very helpful.
Although this was a casual reading, I often found myself, reading one chapter, and having aha moments about something in the previous chapter(s), going back, sketching on paper or on a white board. Overall, even with my limited background in mathematics, I really enjoyed reading this work.