I've never kept count, but I would think my average is about two books a week.
Interestingly, I find that I read more and more books every year, though I've always been a fairly big reader.
That being said, I'm not a particularly fast reader overall. Naturally, it depends strongly on the type of book... A Stephen King or Evelyn Waugh book will go by much faster than, say, Ulysses, but that's natural. I sometimes do wish I was a faster reader though... I find that I can read very fast when I put my mind to it, while still getting the "feel" and retaining what I've read, but my natural, comfortable pace is noticably slower.
The speed-reading discussion here is somewhat interesting to me because of this. I know people who generally are much faster readers, and whose reading experiences probably are no less than mine because of it. Some say that speed reading, up to a point, helps, because of the way you take in the words, sentences and structures.
What I've done the last couple of weeks is have a simply written book (i.e. with rather drab language) that I pick up from time to time and make myself read faster than is my common pace. Why? Training, basically. Pointless? Perhaps, but worth the experiment.
That being said, I don't have any interest in doing what's called "speed reading," I just want to be a fairly fast reader. Speed reading seems to be more about picking out keywords etc and gulping down information, certainly not something for leisure reading of novels, but more practical. I read up a bit on it once (oh joy, how cute) and the techniques include lots of silly tricks like first scanning just the first and last words on each page, then sort of doing a cross-hatch read of the page. No matter how practical it might be, I'm just not willing to attempt it.
Brevity's a charm, eh?