The Works stores seem to have a number of decent deals on game books.
The pick of the bunch is probably the ACIV: Blackbeards Lost Journal for £6.00 but they also had:
Fallout 4: Vault Hunters Survival Guide (Collectors Edition) - £5.00
Batman: Arkham Knight - £5.00
Star Wars: Battlefront Collectors Guide - £7.00
These are all instore deals (the Newcastle Royal Quays store to be exact) but apparently the deals nationwide.
Not to everyone's taste as some folks prefer internet guides, but for collectors/fans of the specific games, these are great prices.
*Edit: Please see the links added by nathan3007 below for the deals online. Thanks again man!