The Leapfrog tag books, RRP of supposedly near £13 have been reduced by the likes of amazon to just over £7, but Boots are doing them for less than a fiver, half their normal price of a tenner.
The above link is for Toy Story, compatible with both the normal tag reader and the junior version. The links below are for Ben 10 and Disney Princesses, which aren't compatible with the junior one.
Ben 10, £5.04http://www.boots.com/en/LeapFrog-Ben-10-Tag-Storybook_985993/
Dosney Little Mermaid, £6.50http://www.boots.com/en/LeapFrog-Disney-Princess-Tag-Storybook_124902/
My little boy got the Reader system for Christmas, and I've ordered the first two above to keep in as rewards for reaching the top of his reward chart.