Each Murders at Karlov Manor Play BoosterBox contains:
36 Murders at Karlov Manor Play Boosters
14Magic: The Gatheringcards per booster
1-4 cards of rarity Rare or higher in every pack
6-9 Uncommon cards, 3-6 Common cards and 1 Traditional Foil card
1 Land card
1 token/ad card, helper card, or art card
Starting with The Brothers' War, Buy-a-Box Promos will only be available for in-store pick-ups and purchase while supplies last as stated in Wizards of the Coast's article here.