Been a long time since I ran this, and I had to go back and skim through it again. You'd be surprised how much you can forget after a year or so -- especially when one has a castle & dungeon THIS large.
It's safe to say that you get a LOT of replay value! It's also safe to say that you'll get a good strong feeling of everything which worked in 1975 - without much of the ambiguity of Those Original Rules. In short, there is both meaning and madness in this setting, and each player will be rewarded for playing in character AND using player strategy. GMs will be rewarded if they study the background and extrapolate further developments - and plant many rumors.
PCs should learn of the rumors, especially, of the creator of this place. This can give them the advantage of guessing (it'll be no more than an educated guess) the meanings and motivations of the designer: the Mad Archmage. PCs should realize that madmen have reasons for what they do - even if the reasons make no sense to sane characters.
For instance, in a nod to That First Dungeon, the dungeon (and maybe the castle?) is still under construction. Signs of the construction crew's work - and maybe the crew themselves - may well hinder the players' characters.
Read the background, take plenty of light sources, and find places to sleep every night (or day) and your PCs may well finally meet that Mad Archmage. And if he makes any sense at all, I would like to hear about it.
This is a good solid adventure or series of adventures, which would easily get 5 stars. One star is deducted for not having the maps included withing the book. I have no problem with purchasing the maps separately (though I have, at other times, run games without using maps...let the PCs deal with the confusion and get lost) but it does annoy some young GMs. But they didn't live in 1975, when the gaming worlds in which we played were more dangerous and, frequently, unknown to even the gamesmaster.
[4 of 5 Stars!]