I rated 3 stars mainly because the book, contrarily to the advertising, isn't for engineers, it is for mathematicians. Is written with a very sophisticated mathematics, where simple things become complicated. If you're an engineer you might not be able to read it, or even if you're are able to, you probably won't be interested in theorems and proofs. Sorry, but I was really disappointed with the book, simply isn't what I expected - a book with fundamentals but in an accessible language.