Spoilers shall abound in this review, just to warn people...
I find myself surprised, depressed, and more than a little intimidated to say this, but...wow, that was really disappointing. I never thought I'd say that about something Alan Moore wrote, but it's true.
It's not all Moore's fault, I have to say. Some of it comes from the fact that LoEG volumes are so few and far between (due to Kevin O'Neill's somewhat deliberate speed of drawing) that each one feels more like an "event" than a story, and DC's delay of the release (due to all sorts of reasons) merely amped up the hype. It's possible that there's just no way that anything could live up to the excitement of the idea of the Black Dossier.
But I do think that some of the fault, and I say this as someone not nearly as talented as Alan Moore, is...well, Alan Moore's. For one thing, the sex. I am no prude. I admire greatly Moore's stance that writing 'Lost Girls' opened his eyes to the idea that human sexuality is natural and healthy, and something that can be included in his stories without shame or fear. But I do think that like any writer who's using a new storytelling technique, Moore seems to be overusing it in his first flush of enthusiasm. Much like Brian Michael Bendis scatters random thought balloons in every panel of 'Mighty Avengers', things like "I like pie," or "Where are my keys?", Moore seems to be sticking sex scenes in just to say, "Look! I'm not afraid to include a sex scene!" (In fact, that's literally the case at one point--a porn pamphlet from Orwell's '1984' is inserted between two other pages, seemingly at random.) The overall effect is more numbing and pointless than erotic. A few years down the road, I'm sure Moore will integrate this stuff better, but for now, it feels clumsy and forced.
But that's not the big problem with the Black Dossier. The big problem is...well, the big problem, to put it bluntly, is that it doesn't make a whole lot of sense. Not the plot, that's relatively straightforward. Mina and Quartermain steal the "Black Dossier", a compendium of secrets of the various incarnations of the League, from British Intelligence, and spend the rest of the book on the run while reading it. But very little of the actual material makes sense.
I suppose I should have seen this coming. Moore has been very forthright in discussing how the LoEG books have been and will be getting more and more elaborate in their "continuity references", working in more and more oblique references to other literary works of the period and using them as plot points. After all, Jess Nevins has published two annotated guides to the previous two mini-series, explaining all the "Easter eggs" for people who aren't walking pop culture encyclopedias. But even so, it's very frustrating to read an entire book that's nothing but knowing winks to things you don't recognize. The original series worked because the "Easter eggs" were just that, asides in a story whose main thrust was broad and immediately recognizable. Mister Hyde, the Invisible Man, Captain Nemo, and Allan Quartermain were major literary characters that the average person could recognize, and villains like Moriarty and the Martians from 'War of the Worlds' worked perfectly precisely because they were legendary villains that the legendary heroes could believably struggle against. (Although even in the original series, the veiled references to Fu Manchu were probably a mistake...but more on that in a moment.)
'The Black Dossier' is full of oblique references and veiled hints at other fictional stories, but that's all it really is. There's nothing for a reader except for the satisfaction of picking out a reference they recognize, or more often sighing in frustration as another obscure character shows up that they've never heard of. And since Moore appears to be hanging his hat on the notion that Jess Nevins will be publishing an annotated guide for this series as well, reading 'The Black Dossier' is a bit like buying a trivia quizbook without an answers section.
Worse, even in the parts where Moore probably wants to make things clear, he can't, because he hasn't learned his lesson from Fu Manchu. Too many of the important characters in the book are still under copyright from their respective authors, meaning that Moore has to make veiled allusions and hope that his readers are well educated enough to pick up the hints. (This was the problem with Fu Manchu in the original mini-series...if you're not familiar with Sax Rohmer's pulp villain, then large parts of the series are downright incoherent.) Admittedly, the key reference (a British secret agent named "Jimmy" who worked with Felix Leiter in Jamaica) is clear enough, but for every reference like that, there's a whole series of plot points that turn on You-Know-Who working with Wink-Wink to uncover the secret of That Famous Place With The Buildings, Get It? If you do get it, you'll no doubt be smiling faintly at the way the references dovetail. If you don't, you'll be wondering why they didn't just bundle the damn book with a coupon for the inevitable Nevins guide.
The ending, on the other hand, is a species of error that we haven't seen from Moore yet. It's all in 3-D, for starters (word to the wise: people with glasses hate 3-D effects, because we have a choice of either missing the 3-D part or sitting with the damn book an inch from our nose because we're nearsighted, for Pete's sake...I suppose it could have been worse, Moore could have persuaded DC to include a vinyl record I'd never be able to play on my CD player), and it takes place in the "Burning Realm", a place that's sort of a walk-in imagination where all these fictional characters can go when they get tired of dealing with the real world...except that obviously some of them can't, because they're not "fictional", except that they clearly are, because "Jimmy" is James Bond, but obviously he's not the right kind of fictional, so perhaps it's to do with being the right kind of fictional, but honestly, this isn't a story that has been doing the meta-fiction at all until now, and ringing it in right at the end of the third book for about ten pages feels odd and takes you right out of the story. The ending feels really like a chapter of 'Promethea' that wound up in the wrong book--don't get me wrong, I like the idea of fictional characters traveling into and out of the realm of imagination, but that's not the concept of 'League of Extraordinary Gentlemen'. LoEG suggests that it's all real, every last bit of it. Having it suddenly be all real except for the bits that aren't and some of them are and they can go into the imagination when they want to so they don't age...it's a pretty severe tangent, and it muddles the message.
I don't wish to sound wholly negative, since even disappointing Alan Moore is still Alan Moore, and there's one short story in there that works perfectly as an example of how LoEG should work (Jeeves vs. C'thullu, a clear example of two iconic and legendary characters facing off on a grand literary stage.) But on the whole, it really came off as self-indulgent and esoteric, and strangely pointless. Perhaps when Jess Nevins writes about it, I'll be more impressed.