The Man who was Thursday is excellent. Have you read The Napoleon of Notting Hill as well?
Oh and on the subject of Catholic lit, I was going to suggest Hadrian VII except I think the copy I have is the last edition that was in print and it's currently hard to find. I'll have to check Gutenberg.
Sod it, I'll flip through one of my copies of Dune and join in. Do you want to stop at the novel proper of include the appendices