Outline - Karl Adam - The Spirit Of Catholicism (PDF)
From the 1950s, pre-Vatican II. This book lays out the basic argument as to why you should convert to Romanism. It will have you pulling out your Visa card to buy your airline ticket to Rome.
This is not so much a polemic against "Protestants" as it is a positive description (by a very intelligent adherent) of the historic Roman Catholic theology. The book is a good resource for the searching layman, but of profit for clergy, too.