Combinatorics research, the branch of mathematics that deals with the study of discrete, usually finite, structures, covers a wide range of problems not only in mathematics but also in the biological sciences, engineering, and computer science. The Handbook of Combinatorics brings together almost every aspect of this enormous field and is destined to become a classic. Ronald L. Graham, Martin Grötschel, and László Lovász, three of the world's leading combinatorialists, have compiled a selection of articles that cover combinatorics in graph theory, theoretical computer science, optimization, and convexity theory, plus applications in operations research, electrical engineering, statistical mechanics, chemistry, molecular biology, pure mathematics, and computer science.
The 20 articles in Volume 1 deal with structures while the 24 articles in Volume 2 focus on aspects, tools, applications, and horizons.
It is probably just me, but I find it a bit amusing when something with enough weight to effectively use it in self defense is called handbook.
It is a good and useful reference if you want to search for something, look up some specific topics or theorems - so if you know (more-or-less) what you are searching. For researchers it is useful to have one at the university, so you can look up things if needed, but if you are not a researcher, just interested in combinatorics, I would advise you to look for other books, because this one is really not meant to be read from cover to cover.