What is the Drop Rate for Tomes?

What are the odds of getting a tome from a random drop? I’m around realm depth 80, not underleveled, and I still haven’t seen one.

I thought Prophecies were supposed to include a guaranteed tome? Instead, I’ve just been getting +1/-1 heredity modifiers, which is kind of uselsss since I could just breed that myself.

Is it possible to get tomes other than buying them from the god shop?

Tomes from random drops are quite rare, but can be boosted with all the loot modifiers. Prophecies do not include a guaranteed tome, but rather a chance to get one (they are rare there too). You can also get guaranteed tomes from the god shops for each favor rank. Goblet of Giving also gives tomes, but isn’t really worth it until normal (not itherian) realm level in the thousands. Shady Dealer is probably the best source of tomes.