I would read that book like I read Harry Potter, repeatedly.

Thank you.

The villain is a necromancer, probably.

SHHHH. SPOILERS. WHOVIAN.

In the book or people reading them?

No, the problem there is that everyone is dead from the start.

But, aren't they already dead from the start?

If I were to write a story like this, when they 'live' their body disappears from that world and they appear in the living world where dying is bad