"The Other Wind" by Ursula k. Le guin

It is the 6th book of the Earthsea Cycle, a series of books where wizardry is real though rarely lucrative or even accepted, depending on which of the many isles you live. 

In this book, all the rules are changing.

Spells no longer work as they should (if they cast at all). Quite a few dragons have disappeared and the remaining ones are breaking their oath by burning down villages and the people's livelihoods, yet they haven't harmed the villagers themselves. 

There is is still no wizard appointed as Archmage on roke island, the isle of wizardry. The only clue being "a woman on gont" but a woman has never been allowed in the school of the wizards, let alone considered eligible to be Archmage. 

And on a darker note, the dead are haunting people's dreams, reaching out to them from across the wall that keeps those who have passed on, in the "dry land" separated from the living and the quiet rest they so desparately crave.