I don't know what system Coventry libraries use, but you can see their info here:
http://www.coventry.gov.uk/info/2000...s/1349/e-books
It's a good system, whatever it is, and you can select the number of days you want the book for - between 1 and 21. They're always adding to the selection, and are very open to suggestions for what people would like adding even though the options are limited. It does seem that the majority of books in their system are Random House books.
Birmingham's digital library uses Overdrive (
http://birmingham-uk.lib.overdrive.com), and allows you to check out 3 titles and to have reservations on 4 titles.
Nottingham libraries used to charge £1 per book. However, it seems they've now scrapped that and they use the same system that Coventry uses (whatever that is):
http://www.nottinghamshire.gov.uk/le...ership/ebooks/