I'm getting a bit canny now at this book downloading lark. Certainly by e-shopping around you can definitely get good value when buying your download books. It pays to look in America. If you have problems using a UK credit card over there (which I did) get a PayPal account. Then it's no problem.
BooksOnBoard is worth a visit. I downloaded Patricia Cornwell's The Front for $5.59. That's £3.38 converted to UK. The same title from WH Smith downloads at £5.13. That's £1.75 more. It's £5.47 at Waterstones.
Sony's e-library is compatible with Waterstones. They are okay as long as you stay off the new release stuff which gets expensive.
But here's where the real savings are. Do you buy a newspaper each day? My wife reads the Daily Mail, mostly for the features and book reviews on Fridays. A Mail costs 50p daily and 70p on Saturday. A yearly total of £153.
Do this: Buy a Sony PRS 505 eReader from Waterstones who are selling them for £179. Download Calibre for free onto your computer or laptop. Tell Calibre to download the Daily Mail each morning and send it to your Sony eReader (it's easy.)
In one year you save your £153. Within months later you have bought your eReader for free! If you read the Daily Telegraph or the Times it gets better. The D.Tel costs £293 per year. You've paid for your eReader by September! Try it with the NY Times or the Washington Post.
Calibre will download for you many other titles such as: New York Times Top Stories, Washington Post, The Guardian, Irish Times, Glasgow Herald or even Al Jazeera and many others. My wife's taken to reading the Moscow Times translation.
It's a whole new downloadable world in your palm - and free!