And I have suggestions of my own to kick things off as well:
Some unnamed Dick Francis book. Because they seem like they'd be for a very targeted audience but... then again, I'm not sure I've heard of anyone who's read Dick Francis who doesn't actually like him! I admit though this is also a bit of, um, moderator bias, so to speak. :p Anyhow, they're also usually pretty short/quick reads, and there's a short story collection in the mix as well. Just a thought.
Elric of Melnibone by Michael Moorcock - Now, I didn't enjoy these books tremendously (in fact, I don't think I ever made it all the way through the series), but on the other hand they're some of the shortest novels I can think of offhand, and classics of the genre, and in a somewhat denser (to me anyhow) style that might reward the sort of close group reading that we're doing here.
Edited to add:
Some volume of Lucifer, which has the double things going for it of being a) a graphic novel (and non-Moore no less), and b) totally awesome. The downside is that I'm not sure how well any of the particular volumes would stand alone, although they are in fairly distinct arcs from what I remember.
Any thoughts on these, yay or nay, or even neutral?