Tanya

[Director Michael]

There is no obligation to do so. Much of it is advanced material that applies only to Jews, and that may be misinterpreted or misapplied if one does not have the prerequisite background and perspective. But the second book of Tanya, "Sha'ar Ha'Yichud Ve'ha'Emunah" ("Gate of the Unity [of G-d] and the Faith") is appropriate for a faithful Noahide to read. If you decide to do so, it is recommended  (if possible) to learn it with an Orthodox Jew who understands it well, and who can explain it on your level (whether you are an advanced Noahide student, or a beginner, etc.)