Re Bettery (sic) life is key
Firstly, the ipad is way more than just a book reader. It can be an eBook reader, but also a Video/ TV player, MP3 player, Internet browser, Email device, Photoframe, portable Games console, productivity device (iWorks looks like it will be usable), capable of running any of the 140,000+ apps already available in the apps store. Heck, it's practically a netbook! Being all of these things, battery life will be compromised on and obviously less than a dedicated ebook reader.
Secondly, the quoted 10 hour battery life was for playing videos non-stop. Obviously battery life would be increased if only using the ipad as a book reader. You could turn wi-fi/ 3g off, reduce brightness, volume etc. which would further increase battery life.
Thirdly, UK prices have not yet been an announced but starting price is $499, which is £314 at today's exchange rate. I don't think Apple will price it at £499.
Ebooks are already here with the iPhone/ iPod touch. Try the Stanza app. Books are downloaded, from several different sources, within the app itself. Don't need iTunes for that. Knowing Apple, the bookstore with the ipad will no doubt be very extensive (and expensive, probably!).
Finally, I'm writing this on an iPod Touch, which is fine. This can only get better with the ipad. Try doing that on your ebook reader!