I first read this book during one of my master degree classes. It was the book that introduced me to the idea behind implementing and/or applying algebraic properties, techniques, and methods to graphs. That's why it was difficult for me to understand some of the concepts and methods when reading it the first time.
I came to this book from time to time when needed, but last year I started to teach MA6281 Algebraic Graph Theory which gave me an opportunity to give a closer look. Overall, it is a good book for graduate students. It gives all the necessary backgrounds and important facts on three big ideas: linear algebra in Graph Theory, coloring problems, symmetry and regularity. It gives (mostly) sketches of proofs, which give students opportunities to think and have a deeper look into some of the theorems.
This book is a classic and so it lacks of some of the new results connected to the field. Godsil and Royle's book with the same title, for instance, gives a more cutting-edge applications.