The Other Wind (Earthsea Series #6) by Ursula K. Le Guin

The wizard Alder comes from Roke to the island of Gont in search of the Archmage, Lord Sparrowhawk, once known as Ged. The man who was once the most powerful wizard in the Islands now lives with his wife Tenar and their adopted daughter Tehanu. Alder needs help: his beloved wife died and in his dreams she calls him to the land of the dead - and now the dead are haunting him, begging for release. He can no longer sleep, and the Wizards of Earthsea are worried.
But there is more at stake than the unquiet rest of one minor wizard: for the dragons of Earthsea have arisen, to reclaim the lands that were once theirs. Only Tehanu, herself daughter of a dragon, can talk to them; it may be that Alder's dreams hold the key to the salvation of Earthsea and all the peoples who live there.