I read The End of Faith by Sam Harris as a preparation for a discussion of this book at the Bend, Oregon, main public library this coming Sunday. The Wikipedia article on Sam Harris gives a good post-view of much of this book he published back in 2004 and it is even more clearly focused on his argument. This first book of his makes clear the observation that there can be no peace in the world with each of the various religions demanding adherence to their particular form of faith. Monotheism is particularly contentious on this point as every individual is inherently different and they each will have a uniquely personal point of view on what the details of God and religion should mean and be. That can only result in interpersonal conflict and group conflict and ultimately religious wars on subtle points of doctrine.
It appears that the Classical Romans had the right idea about separation of state and religion when they legally forbade people from promoting religion and particularly monotheistic religions. They permitted everyone to practice their personal religion and seem to have encouraged everyone to have household idols to their personal gods. The Roman problem with the Jews and later Christians was their proselytizing and thus creating conflict within the body politic. Harris compares the thousand years of Christianity that arose after Emperor Constantine made it a state-controlled entity to modern Islam. Making monotheistic religion into a state entity with a military inevitably creates wars and that is where he finds fault with the current Muslims.
Religion and especially monotheistic religions must be abandoned or humanity which now possesses superweapons will destroy itself.