One of the best books ever written by a Catholic on Protestantism is Louis Bouyer's wonderful book "The Spirit And Forms Of Protestantism". The main thrust of the book is that at the heart of the Protestant reformation lie good intentions and goals that had erred in thinking that reform of the kind needed had to happen by breaking with the Church. In other words, the good things in Protestantism can only be truly fulfilled and attained within the Catholic Church. I highly recommend the book, but with a warning, it isn't light reading.
If you would like to get a good article to whet your appetite, then you can read Mark Brumley's summation of the argument. Brumley is one of my former instructors and is a fan, as am I.