This book is about the Buddhist path to enlightenment, but contains many things applicable to improving anyone's life. It deals a lot with human suffering, and the need for people to help remove the suffering of others, as through this one's own life may be improved.
Although it is presented from a Buddhist perspective, much of the teaching is a good guide to self development, the principles that it teaches are hard to fault, and it remains centered on these things throughout the book.
The commentary deals with the Buddhist philosphies that Santideva uses, and explains the Buddhist principles involved, rather than explaining the teachings.
It gets pretty involved, but you can take quite a lot out of it.
"When the mental attitude of anger is slain, then slain is every enemy"......
Clarification: the book is not as bad as it can be, neither is it as good as there can possibly be. It just is. It is truth/Truth. It has helped many find the path, it can help everyone and anyone if it is read conscientously. Let us put an end to suffering not for our own pityful selves, but for the sake of every other embodied being. Peace.