With their line-up of "World of Darkness" games (Vampire, Werewolf, Mage, Wraith, and Changeling) complete, and even the most detailed sourcebooks increasingly concerned with filling in (or manufacturing) ever-smaller gaps in the background, White Wolf hit on an elegant way to extend the line without too much forcing; they decided to create new standalone games corresponding to each of the five, but set in historical periods of some significance to the supernatural factions involved.
Pushing Vampire back to the Dark Ages was straightforward enough, although this period hardly involves anything new to role-playing, while Werewolf: the Wild West is perhaps more of an interestingly unusual idea than a great one. However, third time out, the project has struck gold; Mage has gone back to the European Renaissance -- specifically, the fifteenth century.
This is a period when the central conflict of Mage -- the struggle between reason, mysticism, and faith -- is much more evenly balanced, and is being fought out in every university, city, castle, and counting-house. Thus, although the book insists occasionally that this is still a horror game, and it has the demons to prove it, there is both a sense of hope and an edge of ironic fatalism leant by the knowledge of where all these bold new ideas and valiant struggles will lead. It's clear that the Order of Reason, which in modern-day Mage will become the icy and ruthless Technocracy, has a lot of justice on its side at this time; the opposing Traditions frankly come across as arrogant, narrow-minded, and self-centered snobs, albeit with ideals of their own. In fact, it is perfectly possible to play characters from either side of the divide, and even to mix the two, given a tolerant storyteller; this would probably mean a lot of fights with demonologists, insane "Marauds", and fanatically intolerant witch-hunters.
Incidentally, the fifteenth century is not part of the Middle Ages; it's a time when medieval ideas and traditions are coming into conflict with dynamic new ideas of exploration, free thought, and world-wide trade. (This is part of the reason why the Order of Reason may prove a lot more exciting to play than the stick-in-the-mud Traditions. They also get fencing rapiers, unreliable firearms, and some really cool Leonardo da Vinci-style gadgets.) The conflict among the Awakened involves some strange alliances, with quirky alchemists, archaic pagans, and the heretical Celestial Chorus among the Traditions, facing revolting-peasant Craftmasons, bold proto-scientists, and fanatical Christian "Garbrielites" on the other side.
One possible objection to the game is that it's seriously Eurocentric; both major factions are based in that continent, and the representatives of other cultures are treated as eccentric outsiders. However, this reflects the fact that Europe is about to explode into an age of expansion and exploration (because of the Order of Reason?); it's the battleground in the war for the future.
The rules and magic system are, of course, those of Mage, with a few tweaks and developments. Most readers will probably know by now whether they like or hate White Wolf's "Storyteller" system, with its relative simplicity and annoying difficulty in working out the chance of success or failure for a given task; however, being a modern WW game, this one at least presents it well, with few glaring holes. Fifteenth-century characters have a certain amount more freedom in their starting abilities than their modern descendents; no spheres are mandatory, and tools (foci) are more a matter of personal choice and style. On the other hand, characters have to be a lot more advanced before they can shed their tools, making for magick which is more a matter of procedure and style, and less swift effort of will. One inevitable but potentially tricky change is that some blatantly "magickal" castings are not considered "vain" (i.e. "vulgar" in the modern-day game's parlance), because everyone believes that such things work -- while much of the Order of Reason's techno-magick is hopelessly vain. This could give some factions a killer advantage over others, unless carefully watched; for example, Christian miracle-workers are always believed in -- but I'd require anyone using such techniques to behave in a remarkably saintly fashion in public, at all times.
Oh, and too much "vain" magick doesn't just bring down "Paradox" -- it triggers the "Scourge", a wildly unpredictable force that can either harm or heal, seemingly at whim. This should turn games into real roller-coaster rides. One oddity is that, although these forces are clearly tied to the belief-systems of the un-Awakened characters who observe magick being used, none of these brilliant, enlightened mages seem quite to have noticed the rules of the game yet...
Incidentally, those who love the setting but don't quite take to the Storyteller system should note that the system conversion provided by GURPS Mage can also be applied here, with a few tweaks and twists. GURPS supplements such as Swashbucklers or High Tech could help enrich the resulting game.
The book itself is nicely presented -- a hardback, quite logically structured and heavily illustrated, it opens with a short (and to be honest, not very remarkable) piece of fiction by Storm Constantine, illustrated in full (and slightly garish) color by Greg and Tim Hildebrandt. And yes, there is an index, with valid page numbers; it would have been a lot more useful at three times the length, but that's partly a sign of the richness of the book. Taking Mage back five centuries could be the most progressive thing that White Wolf have done for years.