I Selected 4 on average, but I tend to buy ebooks in fits and starts, usually when there is a special sale, like Fictionwise and BoB recent ones, then I'll buy 20-30 at a time.
My book budget used to be about £40-50 a month, But i've reduced it to about £20-30 with about half spent on ebooks as I spent quiet a bit on getting the reader whose cost I want to amortise (So I can save up for the next gadget
). The only problem is that Super sales mean that I end up blowing my budget for 2-4 months at a time, though I still have Micropay which I can use over that period.
As for reading, it really depends. If I'm free, it can be a Book or three a day but on average I tend to read 2-4 books a week, but usually at least half are rereads as I like to go over old favourites on a regular basis, especially when a new book in a series is about to come out.