Nelsen does here exactly what he sets out to do. Provide a straight forward and easy to understand introduction to copula distribution functions for the maths-savvy reader. No complex maths is used, just basic probability ideas. The author details the various proofs and theorems that underpin copula theory without getting too bogged down in the nitty gritty (though in some places you sometimes find yourself wanting just a little but more explanation. Not often though and it's not a real problem). Its easy enough to pick up and put down at your will. It's a great introduction to the subject. Probably best used as a text book rather than merely a reference but I don't know - i used it to learn about copulas, and now use it as a reference and it seem to do fine so maybe I'm wrong!) Highly recommended.
Couldn't agree more with A Customer. The style is crisp so that at times you find yourself pausing for half an hour over some line in a proof only to find that it was obvious all along. But that is good. Gets you thinking about copulas. By the end of the book you have a very satisfying intuitive feel for the subject with concepts like the distribution of mass throughout the copula making such heuristic sense. As an actuary working in insurance, this is perfect for my needs.