I am not a fan of alternate-history science fiction. I always imagine the authors as earnest but celibate teenage boys, painstakingly assembling miniature military figurines in their parents' basements. It's basically, as far as I can tell, fan-fic.

   J. Gregory Keyes' "Age of Unreason" series is a huge exception, a rich, dense treat for history fans. It is a brownie in a sea of low-fat Atkins snacks. It is a Guiness in a bar full of Pabst Blue Ribbon.

   Keyes' premise is immediately engaging: Newton's more esoteric dabblings have paid off. Alchemy works. New and devastating weapons are suddenly available to the powers of 17^th century Europe. But what other more shadowy and sinister powers are at work?

   For the most part, Keyes rises to the challenge of his premise, pulling in such disparate historical figures as Ben Franklin, Blackbeard the Pirate, Voltaire, Swedenborg, Peter the Great, and King Charles of Sweden, all of which are handled with such care and depth that they come utterly to life without losing their feel of authenticity. He is equally ambitious with his subject matter, tackling thornier topics than most writers are willing to approach-calculus, Newton's Principia, Jewish mysticism, Siberian shamanism, theology, 18^th century Native American cultures, and the tangled web of European alliances, without veering too much into infodumping.

   And there's more: Romance! Intrigue! Gigantic battles! Mad scientists! Pirates! Comets! Wheels of Fire! The mix creates a story that is both brainy and fun.

   At times his writing takes on great power and beauty, a pause for lyricism and reflection that provides an effective counterpoint to the terse, action-oriented clip of the narrative. One section, a scene of the Russians preparing for a last stand, actually made me cry. The two people who borrowed the books from me cried, too, so it wasn't just misplaced sentiment on my part. Keyes is just that good.

   Sometimes Keyes falls flat-a particularly annoying deus ex machina subplot abruptly arises in the final installment that feels as if had been lifted directly from Dune. It is, mercifully, small enough (and quickly enough dropped) that it can be easily overlooked. Also in the forgivable category are the unwieldy "Previously, on the Age of Unreason" lead-ins, which (of necessity) take up increasingly large sections of the books. I think that if you, say, pick up book three of a four book series, then you deserve to be confused and should not be pandered to. I am sure that the publisher sees things differently, but the no-reader-left-behind back story sections sure get annoying, especially as they feel much more forced that the rest of the story.

   Keyes' books are so genuinely engaging that even the most snot-headed reader (like me-I've been known to take a red pen to my paperbacks) will be willing to overlook the minor flaws.

   I would rather, any day, read a work that aims too high and falls slightly short, than one that succeeds admirably at being mundane. This series should especially appeal to fans of Philip Pullman's His Dark Materials series looking for something new to sink their teeth into.