A month and a half is not long in the grand scheme of things. Sure, some people hop off the boat with hundreds of fans, but for every one person like that there are hundreds of others who take infinitely longer to develop fanbases. So if I were you, I wouldn't be worrying yet.
It's definitely not fun working hard on something, struggling to meet the deadlines you set for readers you don't have.
I think it's really hard for authors if they're only writing for the fans/to get fans. I'm a bit worried from your comments here (and at the other thread about fans), that your focus over the last few weeks might have unconciously shifted towards writing for the fans. Please don't do that -- I've been down that road, and it's a hard funk to get yourself out of. Inherantly, writing for the fans is just impractical. On the larger scale, fans invariably shift/leave and they'll invariably dislike some things you've written -- having a non-fan related motivation helps you to stay centered during these times, and not end up floundering. Fans are great, and deserve their due, but they shouldn't be the center of a writer's universe.
Is there a secret to promotion that I'm just not getting?
Promoting a series is generally something that authors learn through hits and misses. They try some places that don't work, and then try others that do. It depends a lot on each author's budget, content, availability, graphic skills, etc. I like to joke with some of my friends that advertising is almost like an occult mystery -- it can't be taught, and instead it must be learned firsthand.
Is my site layout too hard for people to navigate?
Some slight annoyances I have with your site: the layout's too wide for my computer, and I have to scroll over to read it all. Perhaps you should change your values to percentages instead of fixed numbers, so that it'll work well on all screen sizes. Perhaps also some space between your news updates, so it doesn't just strike readers as a text blob. I'm also not a fan of the white letters on a bright background -- strains my eyes (and I don't have bad vision).
And, erm, why have a FAQ if you don't have anything on it? Either delete it until you get some questions, or make some up to answer (things you think writers might want to know -- heck, some of the questions on your "about" page might even be better suited on an FAQ page). I can guarantee you that's how most FAQ pages start out. If you really want to keep the page blank, than at least include on that page in the "no one's asked yet" area a way to contact you with a question (other than forums, because people don't always feel comfortable asking things on forums).
Another blank area thing -- if none of your creatures yet have pictures, don't put up a spot just to tell us they don't have them. If there's not one there, we can guess that one doesn't yet exist. Instead, just give us the descriptions, and once you've get a good percentage of creature pics done, than make an image column. It looks less empty/more professional that way.
Ditto on the forum. I'd wait on that until you had more readers. As discussed in a different thread, an empty forum can be a turn-off. But that's your decision, and others might feel differently. If you keep it, make a point of adding a way for readers to navigate back to your stories from the forums.
And your nav bar is occassionally inconsistent. There's only one page that allows readers to navigate back to the main page (news section), which is the character guide. Try to keep it consistent by adding the Main tab to the other pages.
Final layout note: not to insult your artwork, but perhaps commissioning someone to do something more professional for the header might help with the audience. People generally only give sites five seconds to draw them in, and an extra-snazzy header might help with that. Though that's by no means neccesary. (*Disclaimer: my wife does art for a living, so I might be pickier when it comes to header art than most.*)
Do I not have enough content?
You seem fine on the having content front. It'd be enough to get me to read through, if I were curious.
Or does my story just need work?
I haven't read it yet, so I'll admit that I don't know if it needs work. Chris makes some general comments in his review, though. If you're worried about that, you might try workshopping it with a RL or online critique group.
I just can't quite put my finger on why I can't seem to garner a readership.
Another thing is that you've only had it up for a month and a half (yeah, I know I said this, but follow me here), which means you put it up around late August/Early September. School started at the same time for your target audience, so not many people were online. Relax...there's a few big holidays coming up, where people will have chances to start reading something new (to pass the time). Take a few breathers, and stop worrying so much about readers. That doesn't mean that you should stop advertising, but that you shouldn't freak out about fans not appearing instantly.
Remeber also: Readers are a fickle bunch. It's quite possible there's nothing wrong with your site, you're just hitting the wrong people at the wrong times. Let time take it's effect. If you're up for three years with no readers, then you can start to worry a bit. Of course, by then I'd hope readers would be a bonus, not the main focus.