I finished the book over the weekend and I must say that I enjoyed it immesenly. I agree that the build up to Batman and Superman was rather slow but it gave KJA time to do a couple of pages on their origins that I really enjoyed reading. There wasn't much action but I figured that this was meant to be a detective novel...both with Bruce using his skills as a detective and Clark as an investigative reporter. This book focused way too much on Luthor and his plan to take over the world. I would have loved if Brainiac was used some how as the villain.
Loved all the UFO references and 50's era references...it really did have a New Frontier, Superman for All Seasons type of feel to it. I can see why Anderson felt it necessary to acknowledge Jeph Loeb and Tim Sale in his acknowledgment page. Overall I would give this a 3.5/5 rating (a much stronger rating than I gave Last Days of Krypton which was a 1.5 or a 2.0.)