You buy 1 box of 12 and you get 1 box for free = 24 bars in total.
The normal retail price of these bars are typical £2-3 per bar but due to it be near the expiry date (Feb/March) they are selling them off cheap.
I've ordered from them and it took 5 days to arrive in perfect packaging, the bars taste ok, but I use them to up my daily Protein intake or as a low fatsnack (I'm a bodybuilder).
This deal has been going on for some time now, so there's only the S'mores and Blueberry flavours left.
There are other bargains on there as well with Protein Bars, so search around :)