Picked this up a little while back in the nice new trade paper edition from Del Rey's answer to Orb, and it migrated up to the top of the "to-be-read" stack pretty quickly. The following review is more or less spoiler-free.
It's a good read. There are a couple of rough patches- the most noticeable are the way the viewpoint seems to float from one character to another in mid-paragraph, making for some occasional pronoun trouble, and the alternation between "Duffy" and "The Irishman" in references to the protagonist- but it's clearly Powers, and as you would expect, it's a different spin on the themes and settings.
The book is set in 1532, and follows the adventures of Brian Duffy, an Irish mercenary in the various wars wracking Europe at the time. The most important of which is the Turkish invasion of Western Europe, culminating in the siege of Vienna. Duffy begins in Venice, where a mysterious old man going by the name Aurelianus (with a habit of smoking dried snakes, one of the odder touches) hires him to guard the Herzwesten brewery in Vienna. After a distinctly odd journey to Vienna, it quickly becomes clear that there's more at stake than the prevention of bar brawls or the preservation of the furniture. Indeed, Aurelianus claims that nothing less than the fate of all Western civilization depends on keeping the brewery safe from the Turks until October 31.
This is obviously not your run-of-the-mill medievaloid fantasy, though it does feature the occasional buckling of swashes. For one thing, everybody has guns- somewhat primitive guns, granted, but guns. For another, other than the Venice-to-Vienna trip, the book lacks the standard visit-every-country-on-the-map travelogue feel of most fantasies: Duffy reaches Vienna on page 62, and stays there. And while there are attacks by flying monsters and a few fantastic beats, the book is fairly short on flashy and overt magic. There's magic, to be sure, but it has the same sort of slightly hallucinatory quality as in Last Call or The Anubis Gates. There are a couple of vaguely D&D-ish references to specific spells and their casting, but the magic that occurs on-camera (as it were) has a wilder, more mysterious quality.
Much of the action takes place in bars or military camps, lending the whole thing a sort of John Myers Myers air (kind of a cross between The Harp and the Blade and Moorcock's The War Hound and the World's Pain, for those who like disconcerting images...). Vienna is besieged for much of the book, but other than a few references to food shortages and one unpleasant death, things don't ever really get dark. Which is, of course, fitting for a book in which beer is the key to civilization.
The plotting is good, though not quite to the level of Last Call. Some elements of the story feel like they've been jammed in with a crowbar, and the resolution of one running subplot is jarringly abrupt and unsatisfying. Everything moves along at an enjoyable pace, though, spiced up with the occasional Turkish attack or bar brawl, so it's easy to ignore the weaker points. Just about everthing comes together at the end, and the resolution is enjoyable and appropriate.
I'm not the world's biggest Powers fan- Last Call was fantastic, The Stress of Her Regard was... not, Expiration Date was nothing all that special, and The Anubis Gates suffers from the same problem as Freedom and Necessity, namely that it's set in a loving depiction of a historical era I couldn't really care less about. But I'd rank The Drawing of the Dark highly- it's not as good as Last Call, but then few books are. If you're looking for fantasy which plays off the Big Themes of fantastic literature, and puts a different spin on them, I'd definitely recommend checking this out.