LibraryThing | Catalog your books online
There is a fine line between hoarding and collecting. Collecting at least gives you an excuse / explanation.
This is a website devoted to lists of books -- as well as interrelationships between books. In addition it seems to have a large collection of discussion lists about books.
Perhaps you have detected a trend with my pleasure with lists? It's true, I admit it that I have a fascination with lists -- especially complete ones.
Time to stop, I have already revealed enough of my private obsessions...