I've had this on the shelf for years and still refer to it. I've heard Denzinger is one that ought to be on the shelf as well, but I've never gotten around to it.

That's one of my absolute favorite Fulton Sheen quotes. Many of you on the MSF know that my wife recently gave birth to our first child, a little girl named Mary Cecilia. If ever we are blessed with a son, he will be named Fulton.

I agree that Ludwig Ott is a must-have reference work. It's fascinating to read (if you have an interest in theology), as the line-up of Scripture, patristic, conciliar, and papal texts is an impressive witness to the unity AND diversity of the Catholic tradition.

But I would second Scott: the next book to add to your shelf is the latest (and truly the greatest) edition of Denzinger. I can't believe how comprehensive this one is when it comes to magisterial documents.

http://www.amazon.com/Enchiridion-Symbolorum-Compendium-Definitions-Declarations/dp/0898707463/

Hey, I know it's kind of expensive ($47.88), but when you consider that it has thousands of pages of entries spanning 2,000 years, it's a good deal.