Mostly, it took me so long because I didn't like it, and of all the Paizo products I've picked up, this is the first one that surprised me by 1) not being at all what I thought it would be when I bought it, and 2) something that I can rarely (if ever) see myself using. Now, the first problem is largely my fault, not Paizo's. If I expect something, and it turns out to be something else, then I have to examine why I expected that. Did Paizo mislead me, or pull a bait and switch? In this case, the answer clearly is no... I just saw the title and expected something else.
Let me switch gears for a moment and make a little philosophical aside. From people who have played 3e, 3.5 or even Pathfinder and no longer do because they didn't like it, I commonly hear a complaint that it's too complex. There are too many rules, and they stifle the creative side of the game. Personally, I think this complaint is complete hogwash, or at least I don't understand it in the least. Does anyone remember the d20 motto back in 2000-2001 or so? I do. "Tools, not rules." That's right. Tools. Not rules. If a rule is too stifling for your taste... ignore it. Here's a few examples.
Many people have complained that coming up with NPC statblocks was too time consuming and tedious. I agree. Why are you doing it, then? I've long been playing with "Schrödinger's statblock"... i.e., it doesn't exist until the moment you need it. "What? You're trying to hit him? His AC is... 19!" Made it up on the spot. He attacks with a +5, and does 1d8+4 damage. Sounds reasonable for a low to mid-level foe that isn't a major villain but just a throwaway action scene? Well, then, if it's reasonable, then that's what it is.
Calculating skill DC's is another one. What a waste of time. I know that the "default" DC is 15. For a low level character with any kind of bonus to the task at all (ability bonus, a rank or two of skill points) that's a reasonable DC that he can expect to hit at least half the time. A DC of 20 is harder. A character better be reasonably good at that activity to expect a success. A DC of 25 is harder still and a DC of 30 is something that only a real expert should even bother with. Why do I need to calculate anything? Pick a DC that sounds reasonable based on that scale, flavor slightly to taste if needed by stepping it up or down a few points, and keep the game moving.
I've never understood the psychological imperative to use rules that you don't like, when you already know darn well that you would like the game better if you handwaved away the detail and just used the skill system structure, or whatever. So when people say that 3e and it's derivatives have too many rules, I say, They're tools, not rules. If they don't apply to the job you're doing, don't use them. Just like you wouldn't use a circular saw to put a nail into a 2x4, you shouldn't use complex statblocks if all it does is give you a headache and there's no real reason to have them. On the other hand, if you want a recurring villain who's tactically interesting to fight... well, aren't you glad that they give you the option to create more complex statblocks? It's silly to resent the presence of something you don't need. If you don't need it, don't use it. And remember that it's almost always better to have something and not need it then it is to need something and not have it.
The only (minor) exception to this is that it does bug me that D&D uses three books to give you the "core" rules. Clearly it doesn't need to; d20 Modern, d20 Star Wars, d20 Wheel of Time, d20 Call of Cthulhu, True20, and other d20 derivatives use the exact same rules sytem (or close derivatives thereof) and manage to fit the entire game in one book. That D&D uses three is a case of rules bloat. While it doesn't bother me that those rules exist, I'd much rather have been able to be more discretionary about which ones I spent actual money on. Give me the core rules in one book and let me decide which supplements I'm interested in. I'd have passed on big lists of spells, magic items and the properties of doors and walls, but probably bought everything you could give me on big lists of monsters.
But that's not really a problem with the system itself and how it's written, that's a problem with how its bundled and marketed.
So, saying that, I'm going to complain about Faction Guide being, essentially, a big, needlessly complex set of rules for something that doesn't need to have any rules. Certainly not rules this "heavy." I don't exactly resent the fact that they exist, because if someone else out there finds this stuff useful, well, hey, more power to them. I do, however, resent that I bought it, because it's of absolutely no use to me.
During the 3.5 era of the game, Wizards of the Coast came up with a template for organizational descriptions. It had all kinds of common headings, and then gave you a bunch of material under that heading. What the organization is all about. Where it's located. What it's goals are. How it's organized. Who some important members are that the players might interact with or hear about. How the organization can fit into your campaign and what you can do with it.
There were a lot of these organizations that appeared in the "back" chapters of the books in the Complete series, but there were others that popped up here and there too. The Black Cult of Amn, from Fiendish Codex I: Hordes of the Abyss is one that stuck with me as particularly interesting, for example. Each organization got several pages of treatment, and enough detail to enable any GM to easily plop that organization down in his or her campaign if it looked interesting.
So, while I didn't necessarily expect Paizo to follow that template exactly, I guess when I saw the title Faction Guide, I certainly expected something along that same style. Paizo have also over the years been well-known for having a lot of good setting material, and making that an important part of their books. So, while like I said, Paizo didn't exactly bait and switch me, I think my expectations of a book that detailed these factions and organizations from an in-game point of view, mostly, wasn't unreasonable.
What I got instead, was only a few paragraphs about each organization, and often quite a bit less than we got even in the main setting book, to say nothing of the more focused setting books on different regions. The Pathfinder Society even got it's own 64 page book (although that's an exception, certainly.) Rather, more than 50% of the text of the book was used to develop a system whereby you could earn points with organizations, and then cash them in for favors.
Now, as little interest as I had in this conceptually, it could have been salvaged if a lot of really interesting ideas were put out there, but for the most part, these favors that you can "buy" are pretty banal. An expert can make a skill check for you. You can get low and mid-level spells cast for you. You can get mundane equipment, or the loan of minor magic items. Stuff like that. Do I really need a system for this?
Again... trying not to resent the fact that the system actually exists, because some people, especially in the organized play Pathfinder Society, probably do find this useful. But for me? Meh.
That said, I did actually read the system and most of the benefits for most of the organizations, before I was just too bored beyond words to continue and started skimming. You get the points by doing things that further the goals of the organization. And then you spend them. As with hit points, you have a maximum number of points, and then you have a current level of points that is probably below your maximum. You can also buy access to a higher maximum, and you can also burn points off your maximum total for really big favors.
The system seems to be reasonably solid, and would work very well if for some reason you needed to systematize this, but I haven't (and won't) actually playtest it.
Meanwhile, the book that actually gives us some real meaty detail on these organizations remains elusive. I'll keep my eyes open for that going forward, and sadly, have learned to be a bit more discriminating in what Paizo material I pick up rather than buying stuff site unseen just because the title sounds good.