I'm searching for some clarification for the rule "Became a Believer" (Ch. 9 - Magic, page 179 of Italian edition CoC 7e manual).
The explanation in the manual is quite unclear. This is what I’ve understood:
Example PC: Harvey, Current SAN 60, Max SAN 99, Cthulhu Myth 0%
Myth Book: Cultes des Ghoul, Cthulhu Myth: +4/+8, SAN loss 1D10
Harvey does a first read of the book.
Keeper: “Do you believe?”
Case 1: “Yes.”
Harvey loses 1D10 SAN: he rolls 4. He gains +4% Cthulhu Myth, max SAN 99-4 = 95.
Case 2: “No.”
Harvey gain +4% Cthulhu Mythos, max SAN 99-4 = 95
Harvey then reads some more books and gets a total Cthulhu Myth 10% and max SAN 99-10 = 89.
Then some time later Harvey sees a Myth Creature, loses SAN for this and Became a Believer, Harvey also instantly loses SAN equal to Cthulhu Myth (10).
Then all malus of huge sanity loss (>5) are applied.
So the pro of not became a Believer is that the PC doesn't lose SAN reading books but the con is that he will probably lose later, all at once, probably at a bad time.
Is that correct?