A Calculus of Angels, the second book in the "Age of Unreason" series by J. Gregory Keyes, does exactly what a second book is supposed to do. It builds on the first book, giving us more insight into the greater problem that the series addresses, as well as moving all the characters forward. The alternate history that Keyes has built is fascinating stuff, much richer than the “what if World War II turned out differently” that many authors use. A Calculus of Angels is a wonderful mixture of sorcery, alchemy, and science. Keyes also adds a few more characters to the mix, making for a much deeper story.

We are a few years removed from when the great comet hit London and wiped out much of Western Europe. Those in the Americas, not having heard anything from Europe in quite a while, are ready to join forces (French, English, and Native) to send an expedition to find out what is happening. Meanwhile, Peter the Great, Tsar of Russia, is on the march to conquer what is left of Europe. Sir Isaac Newton and his young apprentice, Ben Franklin, are in Prague, attempting to figure out what is really going on. Adrienne, former lover of King Louis of France, is on the run from the remnants of the French nobility, all vying for what’s left of the French throne. What spirits are using the world to fight their own war against humanity? Are these spirits religious in nature, servants of God? Or are they trying to fight everything that humanity holds dear? Who controls whom? And will Peter be able to conquer everything in his path with the mysterious flying ships that he wields? All will come together in one city, one fatal encounter that could decide everything. And what does Adrienne’s child have to do with all of this?

A Calculus of Angels is a much better book than Newton's Cannon, mainly for its broader scope. The first book was pretty narrow, concentrating mainly on Adrienne and Ben Franklin. This one covers a lot more ground. Ben and Adrienne are still prominent, and they get a lot of development as Ben chafes under Newton’s refusal to tell him what Newton is researching and Adrienne learns her place in this spiritual war. But Keyes gives us more storylines to follow as well. There is the expedition from the Americas to discover what is going on, giving us a wonderful character in the Choctaw shaman, Red Shoes. It also gives us Cotton Mather, Blackbeard (former pirate and now governor of a small colony) and the French governor of Louisiana, Bienville. It is through them that we see most of the devastation that covers Europe, especially Great Britain.

While Mather is a bit of a stereotypical religious figure, he does have his surprising moments. The others aren’t quite as well-drawn, though they serve their purposes well in supporting Red Shoes and getting him where he needs to be. Especially good is the scene where some of the ship’s crew take Red Shoes for a night on the town, and he sees the deadness in the girl that is given to him, even as the others finish their night of debauchery. This highlights the other world that only he can see and gives us a great bit of his character.

Probably the best scenes in the book, however, involve young Ben as he tries to make his way in Prague. Newton is being very uncooperative and Ben is trying to do his best to fit in. He is an intelligent young man himself, and he’s invented many toys for the King to play with, but he knows that Newton is holding something back. The interplay between the two is wonderful, especially in their final scene together as Newton realizes just how much he has hurt Ben. Once Ben and the others leave Prague, it’s not quite as interesting, and the scenes in Venice drag a little bit. Still, he’s the most important character in the book, and he carries it well.

The only thing that really mars the book, and it’s a small thing, is how everybody ends up in the same place at the same time. Considering the number of storylines that are going on, this stretches the coincidence just a little too much. Once they are all there, it makes for a riveting conclusion as Ben tries his best to outwit his opponents and survive himself. The ending is a bit predictable, but it leads into an epilogue that really makes you want to read the next book to see where the story goes from here.

One aspect of Newton's Cannon that I hated was the way Keyes began chapters in the middle of action and had the characters reflect back on what happened to catch the reader up. Keyes still does this occasionally, but it’s not quite as noticeable this time. This really adds to the strength of the book, as the prose flows a lot better. The prose is rougher than it is in Keyes’ "Kingdoms of Thorn and Bone" series, but it’s earlier in his career so a bit more acceptable. Keyes has taken an interesting premise and spun half of a very interesting tale. I’m looking forward to the next one.