Been tempted to buy this game from my mate who already has it and has been raving about it. Was looking into prices and came across this as cheapest price I could find. I also had a few quid in credit on my Microsoft account, so worked out even cheaper for me - something to consider if you also have credit on your MS account.
Game is of course a digital download from Xbox store.
But for those who prefer a physical copy, Amazon were offering physical copy for £14 when I checked just but if you're not fussed then I think Xbox store is currently cheapest.