I think it's strange that people seem relatively happy to pay £15 or so for a trip to the cinema, yet seem to complain sometimes at paying £8 or £9 for a paperback. (Edit: just seen Mazarkis post this comparison too, I feel validated in my thought patterns

)
From what I've seen I think, generally, people would be happy to pay £7.99 for a regular paperback if that was how much they cost everywhere, but if they can get it cheaper in Tesco or on Amazon then they will. The net book agreement, broken a few years ago, used to mean that books couldn't be discounted but there were downsides to that, but without it it means that supermarkets can sell them as loss leaders or at cost.
Personally I'm happy to pay for books, if I can get hardbacks I often will - I think it's worth it. I'll pay full price to keep bookshops on the high street too, and also for the convenience of having the book "right now" over "3-5 working days". I pass no judgement on those who buy books as cheaply as they can though, because times are hard.
I think it's worth remembering though, when thinking "oh, I can get this cheaper on Amazon," that £7.99 or £8.99 isn't a markup, it's rrp, so don't feel badly toward the bookshops that are charging that
