Very strong cover art. I'm jealous!
Font size is right at the edge of legibility at the table. I would probably pop the font up a size and turn the descriptive paragraphs in each encounter area into short bullet points instead, given that space is at such a premium in this jam. The font size also seems to change page to page, sometimes even within a page, which makes it look less polished than it deserves.
Good map with meaningful choices, including a passage that only the tiniest characters can get through.
I worry that if every corpse but one punishes players for inspecting them, the players will just start walking past the corpses, making those rooms effectively empty. (Dead crawlers don't get to turn treasure into XP via carousing back in Luton.)
The premise for this adventure is pretty good, Appendix N-wise -- venture into the dark with a glowing crown and put it on a statue to banish the darkness for a year -- but I'd like to see the weird and creepy tone cranked up a bit more to match the solid idea. Check out the novella Black God's Kiss by C.L. Moore, if you haven't, for an example venturing into a very scary dark realm.
Good straightforward adventure that could be taken to the next level with a few minor tweaks.