It seems to oscillate between no. 2 and no. 3. I saw it as No. 2, then later as no.3.
http://www.amazon.com/exec/obidos/tg/new-for-you/top-sellers/-/books/all/ref=b_tn_bh_be/103-7858909-2929445?%5Fencoding=UTF8
It is no. 3 right this minute, but that's still pretty darn good.