Assasin's GateGeorge Packer
Packer was an earlier supporter of the war in Iraq, and for that, he deserves to get called out at every event he speaks at. But, he is also an incredible writer, and Assassin’s Gate is the best written book I have read on the war. Packer moves between DC and Iraq from the beginning of the plans for the war to the (almost) present, and you can feel his disgust with the Bush administration grow and his hope for Iraq fail as the book progresses.
Assassin’s Gate is an excellent read, and a good primer on the basic outline of the lead up to the war, but where the book really shines is in the profiles of people caught up by the war, whether that’s anti Saddamist Iraqi exiles, US soldiers, or young women in Baghdad. It’s a popular book, so you’re not going to get all that much depth, but the personal stories make it well worth the read.