I've now played through all 3 of the Scarthey solo adventures for 5e and can comfortable say that Companionable Darkness was both my personal favourite and probably objectively the best entry in the series.

Companionable Darkness has the most fully realised story in the series as well as a number of NPCs for the PC to interact with. The story itself was engaging and started off a little grey before moving into more traditional black-and-white good-vs-evil territory. I also really enjoyed the more detailed entries and the fact that it felt like this time out the backstory of the adventure was more than tangentially linked to the University Of The Arcane.

I enjoyed Companionable Darkness and would definitely recommend it but there were 2 minor issues that I felt should have been caught in the editing or proof-reading stages:

1. Entry 53 is formatted incorrectly. It starts off mid-sentence and then at the end of the text block you find the missing text from the beginning of the dialogue.
2. Entry 38 tells you to make a DC 13 Wisdom save then offers you two choices neither of which are affected by the outcome of the save.