My big downfall this year has actually been paperbacks. Particularly second-hand crime paperbacks.
Crime is not one of my main genres - I've always dabbled in it a bit, but I'm mainly an SF&F reader, I'd say - so I'm not so bothered about getting good quality books to keep, and I don't want to pay a lot, but lately I've been consumed with enthusiasm to read some of the classics, particularly from the Golden Age, and I've also set myself a challenge to read a detective beginning with every letter of the alphabet. I also like to get out of the office at lunchtime, and a visit to a charity shop or second-hand bookshop is as good an excuse as any. (Agatha Christie is great for this - the tiniest charity shop is still reasonably likely to have at least one book by her.) Just yesterday I bought two omnibuses containing five new novels (and two duplicates). I'm miles ahead of where I need to be, and for some reason I seem to prefer to buy several books in each series instead of just one.
On the plus side, I have also been getting rid of paper books. Charity shops are quite good for that, too.