Here’s a business idea for the budding entrepreneur: a computer book version of “DVDS365″:http://www.dvds365.com/, “ScreenSelect”:http://www.screenselect.co.uk/, “Video Island”:http://videoisland.com/ and “Mailbox Movies”:http://www.mailboxmovies.com/ (flat-rate DVD rental sites). There’s enough interesting computer books coming out at present that I’d like to read, but probably wouldn’t want to own a copy of. Computer books also cost way too much to buy on the off-chance.
So, a flat rate monthly subscription, allowing you to keep 3 books out as long as you want sounds ideal. Throw in the option to purchase, and you’ll have a happy audience 
The postage would cost a lot more than DVD’s, which might mean it isn’t as viable, but maybe there’s a way round that.
Oh, and the books I want to read can be found on “my Amazon wishlist”:http://www.amazon.co.uk/exec/obidos/registry/3v0uy1qfgc97j (purchases gratefully received ;))