Hey, folks. Back from GenCon, exhausted as all heck, and my feet are in more pain than I would think possible with a mere 10 toes and two heels. (I committed the cardinal GenCon sin of only bringing
new shoes with me.

)
But I wanted to chime in on this. See, Andy Collins gave me permission to share one (and
only one) piece of specific information on the
4EToH. And that is this:
The reason that it has such a wide level range is that it's
not a single, play-all-the-way-through-and-stop adventure, the way most published adventure products are. Rather, it's meant to be spread out throughout the length of a campaign, as an ongoing plot arc to which the PCs return time and again. For instance, they might play through the events of the first part at one level, then gain a handful of levels via completely uninvolved adventures*. Then, they experience something that draws them back into the ongoing plot, and go through the second part of the book, and so forth, learning more about the ultimate schemes and objectives of our villain during each step.
*I say "uninvolved adventures," but the DM can certainly choose to link them to the ongoing
ToH plotline if he wishes.
So ultimately, it's less a
single adventure than a number of linked adventures that form a recurring plotline, much like you'll see villains and plot points recur in a TV series. (The Shadow involvement in
Babylon 5, for instance.)