Waterstones (High Street stores only, not online) currently have 3 for 2 on all Games Workshop Black Library publications including RPG rulebooks, hardbacks, and novels. The system works out the cheapest three so if like me you buy 3 £9.99 titles and 3 £6.99 titles you will get one £9.99 one free and one £6.99 one free.
This is a good chance to get stocked up on these titles which rarely ever see High Street price cuts, and whilst Amazon have some of these at equivalent prices they rarely have good availability.
No idea when it ends but it only started this week at my local store in Derby.
Recent releases are there inlcuding Battle For The Abyss, Nagash, etc