Which artifacts are best to equip a hero with?

I prefer books to shields.

And this is important! I personally feel the same way, but given my passion for Archmages, I think it's understandable. However, books certainly won't help in every situation... That's a drawback. No shield can replace the "Book of Demons" or the "Archmage's Codex," and even sometimes, the "Book of the Apprentice" can't be replaced.