Yes, we do that around here. I used to work in a bookstore right after college, so that was a bit funny. There was the time I read a good chunk of the gardening books, organic food gardening mostly, but design and other types of books were read as well... I ended up knowing a pretty large number of plant names sort of by accident. It is pretty funny to me that I can walk through an unfamiliar garden and still name a lot of the plants.
Ds has done this with yu-gi-oh cards most recently. When he was very little he had a dinosaur thing. Mostly this is in the form of reading certain books over and over, looking at websites, videos, etc.
Dd has only been on the earth long enough for one obsession, ballet/nutcracker, but she's really working it. Books, videos, cds. Over and over.
Dh is on a food thing, with little mini-blocks where he'll read alot about and then work for a few weeks on a particular dish. (Cooking and retrying with slight variations)
Right now he is working on a really cool bread recipe that he found, and also some amazing lentil soup. Perfectionist, too.
