If you are someone just trying to learn computational chemistry and if you have some background from Quantum Mechanics this book is for you. It starts with 2 chapters of review of quantum mechanics including matrix notations,spin operators,many electron wf etc.If you have not seen these subjects in quantum mechanics you will probably cannot follow the subject.(If you do not have a background you can learn necessary quantum chemistry from Pilar's book) The most important chapter is the 3rd one- Hartree Fock which explains how does a HF calculation operate.Writers just take He+ & H2 and show how is the calcuation done.You can learn what is electron density, exchange correlation and any other basic terms from this chapter. The next chapters are configuration interaction,pair theories , many body perturbation theory and Green's function. The chapter with perturbation theory is really good and explains most of the core of the subject. This book is always takes as a holy book because it is one of the first qc books that tries to examplify what do the computer programs calculate in such long periods. It compares the methods their efficiencies in determining geometries,energies,etc. If you have a backgorund and want to learn qc you should start from here.Another book in the same level that I can recommend is the Lecture Notes In Quantum Chemistry (Ed.Roos). If you do not know anything about computational chemistry probably the first book you have to read is Jensen. It becomes really annoying if you do not have any background when reading this book and learn nothing but you have to start somewhere and after you get familiar with the terminology you can circle around jensen-pilar-szabo-roos learn subject and feel confident to apply the methods. If you do not want to learn the background but just methods and learn how can you calculate geometry, transition states, etc just the way to apply computational methods to chemistry than my recommendation is to read jensen than two books of Hehre "A laboratory book of Computational Chemistry" and "The Molecular Modeling Workbook for Organic Chemistry" which the later two are only available at wavefun.com. . Returning back to the subject of the review, some can say that this book gives just ancient methods and does not explain how can someone learn how to compute chemistry in 24 hours.I am sorry that any branch related with quantum cannot have an idiot's guide because it needs a deeper understanding. I think people cannot use the qc methods in their jobs without understanding how can they calculate H2 at first.