Deep Secret (Gollancz)

Rupert Venables is a Magid.

It's a Magid's job to oversee what goes on in the vast Multiverse. Actually, Rupert is really only a junior Magid. But he's got a king-sized problem. Rupert's territory includes Earth and the Empire of Korfyros. When his mentor dies Rupert must find a replacement. But there are hundreds of candidates. How is he supposed to choose? And interviewing each one could take forever.