Emily is going home from the library when she's abducted into another world by a necromancer who wants to sacrifice a "Child of Destiny" who has yet to master magic.
Well, her mother's name IS Destiny. . . .
A powerful sorcerer rescues her and then, because she is magically powerful and it's not easy to send her back (and he's not good at teaching apprentices), sends her off to school on dragon back.
Many things ensue. The care necessary for alchemy, the marches of Martial Magic (and the importance of considering your supply list); the difficulty of accounting, and the idea of double-entry bookkeeping and Arabic numbers; a feud with a princess, a kidnapping, and many others.