[By the way, I really wanted to title this post, "Yes, I have an addiction" but I was afraid there weren't enough Dexter fans out there to get the reference.]
This is not a new problem. I've had this problem for many years, in many cities, and over time it has manifested itself in my 600+-book collection (I know, it's not in the thousands or anything, but I've been young and working for peanuts for much of that time. And I still regret getting rid of a number of my books after college and in Boston). My addiction to collecting books on the cheap has been fed primarily at the New England Mobile Book Fair (which is outside of Boston and not at all mobile, in case you're curious) and at the Strand, which is one of my favorite places in New York, and possibly the planet, but also at numerous used bookstores, public and university libraries, and yard sales.
I thought things would be under control here in Shanghai, because I'm back to not having a salary, and English-language books are both hard to find and expensive here. I knew I'd still want things to read, of course, so not knowing what might be available from the library system, I connived, through various means, to assemble a small collection of about 20 of my books from home here.
Then I happened to be in the Western supermarket this week (only the second time I've been in almost two months; not too bad, right?), and there was a sign on the bulletin board about an American Women's Book Fair (sale), proceeds to benefit charity. This weekend! I thought I'd go browse, maybe see if they had any other upcoming expat activities or events that might be interesting. So I trekked out to the other side of the city -- which turned out to take even longer than I had anticipated, as I emerged from the subway only to find that I was still over a mile from my destination.

The good thing about getting to book sales late in the day is that they tend to slash the prices. In this case, the sign outside the book-sale room said things were 50% off. When I got inside, I was told that actually, they were at the "fill a [shopping] basket for RMB20" stage. RMB20! That's less than US$3, even with the falling exchange rate! I probably would have paid RMB20 for just two of the books I picked up -- (Jonathan Franzen's The Corrections and Jon Stewart's Naked Pictures of Famous People), so really, it was like everything else was free. Talk about being enabled!
So as you can see, I returned with some good loot, about twenty books in all (RMB1 each!) -- some fluff, but I also bought some "good" books, including No Country for Old Men (since I'll probably never get around to seeing the movie), A Man in Full, The Virgin Suicides, and Angela's Ashes. Now the only problem is that I have no bookcase (nor really a place to put one)...