I always been curious about tomes but never tried because I sold every amulet but now Quentin being the weekend quest. I thought let's the ones I have in my vault. In total I have used 9 amulet's and got two tomes (Death and Fire).

But now I'm wondering what happens when I give these to my pets? I thought they were just books but they are not not. Also does every tome do something else?

You can get different tomes for different amulets. So a Fire Amulet will give you a Tome of Fire if you're lucky and so on. From Subetalodge:

Thank you for your answer. I thought each tome had its own effect on a pet like a fire tome would power up the fire spells and so on.

According to subetalodge they all seem to give the same stats c: (But I've never tried using one myself^^) Some tomes seem to be ingredients in scroll making though^^

Never knew that. I'm going to use one soon so hopefully it will give me some nice stats. (I'm really new in battling)

That's also good to know! I will search that up before I use them Thanks again!