in one of the pictures on the right side before click download there is a image of a book tome thing in his off hand that makes explosion i believe how do i get one?

You have to fight higher level enemies. If you want to cheat you can use the console by pressing enter.

what kind of enemies drop the magic tomes?

All enemies, I think. They just need to be a high level. I got some spells at level 8 or above, so start there.