I listen to a fantastic (in my opinion) podcast called Books on the Nightstand. In their most recent podcast (linked here) they talk about how sometimes people fear giving books to big-time readers because they don't know their specific reading interests, don't know which books they've already read, or some other road block.
I ran up against this Monday night when trying to buy a work anniversary gift for one of the nurses I work with. I know she loves to read, we talk about what she's reading--right now she's on a classics kick--but I don't know what she's already read or bought (and plans to read).
It was weird because I used to think that I, being a big reader, would always love to get books as gifts because you just couldn't go wrong. Now I realize that may not be true because: 1) I have a TON of books I've already bought that are on my shelf to be read and it would be a waste of your money to buy me one of those; and 2) I am particular in what I read and it's likely to be a waste of your money to buy me something just on a whim at the store.
That being said, I maintain my GoodReads.com account with a category called "Wish List" (books I want to read that I haven't yet procured). Is it in bad form to direct people to that for gift ideas? Does that take the fun out of gift giving?