Catch up (or get ahead and spoil yourself!) in time for the start of Season 7.
This sale is a regular thing every few months at these prices. It's worth checking the Kindle prices (which also include a Comixology copy) but they are currently higher.
Comixology also offer bundles. The #1 - 48 and #49 - 96 bundles are currently better value than the individual volumes at £27.99 but the #97 - 144 bundle is slightly more expensive at £33.99 (£4.25 a volume).
N.B. Amazon are currently offering the Kindle version Walking Dead Compendium Volume 1 (#1 - 48) for £20.23 which is even better value (£2.50 a volume).