The artwork here is absolutely gorgeous! The layout is quite aesthetic while remaining fairly functional as well.
It would be nice though to have some tables or more bullets throughout the text, to improve on-the-fly readability.
It is mentioned near the beginning that a d4, d6, and d8 will split up between the 3 stats, but this can be confusing when seeing 6 stats in the respective section. I understand that 3 are for the parasite and 3 for the character, but this could be explained better.
All 6 stats are introduced, but it is not immediately apparent which stats are for parasite and which are for the character. It becomes more clear after reading things more thoroughly, but this would be an excellent place to have a table. Either have two tables side-by-side, which one being the stats for the character and the other being the stats for the parasite, or perhaps have a single table with one set of three being shaded to distinguish the difference.
Overall I like the concept and I think this could make for a good game, but would hope for some tables or bullets to be added to help for easier understanding and quicker reference at the table.