The big question in a series like the Secret series, where you set up a big mystery, especially one like "the secret of eternal life", is how you handle the revealing of the secret. Do you not reveal it and leave it a mystery, or do you reveal the secret and risk it being a let-down?* Without getting into any spoilers, I think You Have to Stop This handles the problem just fine.
FuzzyCo grade: A-
* cf. the "best singer/artist/poet in the world" problem in movies.