Below, I have summarized my findings by listing a few key examples for each point. They do not cover everything, but they highlight the bases for my review.
Overall, the story is good and clearly written. It faithfully adapts the story of the Gulthias Tree with vivid flavor text and detail-oriented environmental descriptions. Some phrasings are a bit off, like "steady trickle of stagnant water," but word choice is generally good. Behavioral descriptions and battle strategies are concise and clear.
There are quite a few typos and other grammatical errors that distract from the content. The most common is the use of "it's" instead of "its," though there are several sentence fragments and other errors.
The author provides a diverse array of additional resources, such as maps, music suggestions, and optional table mechanics, that are awesome for a number of reasons. Having maps to go with makes DMing over things like Roll20 much easier. Saving time on finding background soundtracks is hugely beneficial for DM's that choose music for ambience. I haven't seen table mechanics represented before in an adventure like this, the concept is fascinating and leads me to think of problem resolution in a new, thematic way.
The adventure provides many variants to RAW for certain situations, which wouldn't be a problem if these rulings were distinguished. The conditions listed for reference vary from hazily worded to flat-out wrong, with Grappled being the prominent example. Additionally, the falling damage for the pit is calculated incorrectly, among others. Druidcraft being cast on the door grates on me because the spell very clearly states the options it can provide; a literal interpretation of the door's triggers declares that setting the door on fire is dangerous unless it's done with druidcraft.
All in all, the adventure is good but can definitely be improved. From a playability standpoint it's solid, but there are a few kinks to iron out before its potential truly shines.