Charles C. Mann 1491: New Revelations of the Americas Before Columbus is an award-winning and excellently written book that debunks a lot of myths about American colonialism and the indigenous people that were there. He also wrote 1493: Uncovering the New World Columbus Created.

Highly recommend getting some Vine Deloria Jr. in your diet: Custer Died for Your Sins is probably his most well-known book. If you care about religion. God Is Red might be compelling to you.