However if you really want to learn the details behind the calculations the following books may be useful
1.Exploring Chemistry With Electronic Structure Methods: A Guide to Using Gaussian by James B. Foresman and AEleen Frisch
2.Introduction to Computational Chemistry by Frank Jensen
3.Computational Chemistry: Introduction to the Theory and Applications of Molecular and Quantum Mechanics by Errol G. Lewars
As per my experience I can tell that Gaussian is one of the most user friendly and well written package out there.There are a lot of calculation/methods are implemented within the package which you can perform with extreme ease. Also number of users are huge,so getting help when in trouble is not a big issue.
However if you really want to learn the details behind the calculations the following books may be useful
1.Exploring Chemistry With Electronic Structure Methods: A Guide to Using Gaussian by James B. Foresman and AEleen Frisch
2.Introduction to Computational Chemistry by Frank Jensen
3.Computational Chemistry: Introduction to the Theory and Applications of Molecular and Quantum Mechanics by Errol G. Lewars
As per my experience I can tell that Gaussian is one of the most user friendly and well written package out there.There are a lot of calculation/methods are implemented within the package which you can perform with extreme ease. Also number of users are huge,so getting help when in trouble is not a big issue.