I'm glad he came clean, but it's a little late now. The damage has been done, and he helped do it. I don't think he'll ever be able to clear his conscience, which seems what he's trying to do. (I heard him on the news tonight in an interview with Katie Couric.)
At least he's made a record of the Bush Administration's behavior. Maybe that will redeem him in the long run. (I haven't read his book.) See Digby's take on it at Hullabaloo.