What if Isaac Newton had discovered that alchemy works? J. Gregory Keyes has based his Age of Unreason series on an alternate 18th century shaped by a "science" that grew from Newton's discovery of "philosopher's mercury," which "can transmit vibrations into the aether" and thus "alter the states and composition of matter." In A Calculus of Angels, Keyes continues the tale he began in Newton's Cannon. It's a satisfying sequel that nevertheless leaves the reader impatient for the next book. Two years have passed since the asteroid struck. The weather is unnaturally cold, the skies perpetually overcast. England is devastated, the French government has collapsed upon the death of Louis XIV. Peter the Great, now inspired by the guardian spirit who preserved Louis, has marched his armies westward into the Netherlands and France. In the New World, the abandoned colonists send a delegation including Blackbeard, Cotton Mather, and a Choctaw shaman named Red Shoes to find out what's happened. In Prague, Newton and his apprentice, Ben Franklin, seek to protect the city from aetheric attack. The mathematically gifted Adrienne de Montchevreuil is also back and expanding her knowledge of the mysterious malakim who inhabit the aether and menace mankind. Keyes creates a very believable mixture of history, fantasy, and plausibly imagined historical characters. Each book has been exciting, suspenseful, and beautifully written. No admirer of alternate history should miss th