When we last left Eddie and Molly, Eddie was dying of an alien poison administered by the infamous and mysterious Dr. DOA, who we found out was actually Eddie's doppelganger, Edmund Drood, from an alternate dimension where he had killed all of the members of the Drood family on his world. He tricked Eddie and Molly into going after him via the Merlin Glass and they wound up in his reality, stuck and with no way of escape, with Edmund doing God-knows-what in the Drood Family Hall, passing himself off as Eddie. Fortunately, the pair isn't stuck for too long.
In traveling through Edmund's version of Drood Hall, they make some startling discoveries and realize that these Droods were way worse than Eddie's family, if that's even possible, and they encounter a being that is mysterious and secretive, and quite possibly very dangerous, but one who is willing to help them escape. Once back home, Eddie and Molly connect with an old man named Peter Drood who knows an awful lot of stuff he shouldn't, mainly because he is the last of the living "very-secret agents" who are trained to do whatever it takes to get the job done, even more so than what the typical Drood is trained to do. It seems Peter has some pretty important knowledge and a few ideas about stopping Edmund, but they involve creepy things like Angelic and Demonic Droods (what could go wrong, eh?), the Museum of Unattached Oddities (a place so dangerous that it doesn't even need staff to protect its contents) and the worst of all, an ancient and dangerous Drood named Gerard AKA Grendel Rex, who managed to turn himself into a god and who now lies trapped by the Drood family way below the depths of Siberia, just waiting to exact his revenge upon the family. Edmund always seems to be one step ahead of Eddie and Molly, and since Eddie is already dying and going about it pretty quickly, it will literally be a race against time to see if they can stop Edmund from destroying all of humanity, all the while doing it from the surface of the moon because, why not?
Although I really enjoyed Moonbreaker and was glad to see how the story wrapped up, once again I felt like I was behind the eight ball as so many old adventures and characters were referenced. Since I have only read one other book in the series, and I just discovered that the next book, Nightside, will be the final book in the series, I was kind of sad that I hadn't discovered Secret Histories years ago. If you want to get into the Secret Histories series, don't do it with this book. In fact, start at the beginning. The characters are endearing, fun and adventurous and I think I would really enjoy getting to read about all of the adventures that Eddie and Molly reference. They are one wild pair and I imagine the journey getting to this point is one best read in order. That said, I enjoyed Moonbreaker even more than Dr. DOA.