I legitimately really like this adventure. It's got a lot of awesome twists and turns and NPCs. It's got mysteries, conspiracies, and paranoid wizards. From an adventure design, I think this is phenomenal.
The only gripe that I have with it has to do specifically with its "5e" designation. It's clear that this was written for a retro-clone whenever a magic-user's tactics are described because it doesn't take into account 5e's concentration restrictions. For example, before ambushing the PCs, one wizard is supposed to cast alter self and fly on himself and then use black tentacles in combat. This doesn't work at all with the 5e version of these spells as casting one would end the previous spell, not to mention that Swords & Wizardry spell times are significantly longer than 5e spells. So be forewarned that if you hope to run this, you're probably going to have to find some kind of work around for these encounters.