for a first book i would definitely go with little green book by Phil Gordon, i would also go with crushing the microstakes by Nathan Blackrain. For a more advanced thinking i would proceed with math that matters by Oven Gaines, and definitely when you get all the basic concept from Phil Nathan and get with the math by oven i would go to Easy Game by Baluga whale and Aplication of NLHE by Janda, that would be the exact order of the books i would recommend to a cash player, add to that the donkr series on 3betting by bugs...