Prydain Universe

Taran is an Assistant Pig-Keeper, which is exactly as grand as it sounds, and the pig is an oracular white sow who will not tell him what he wants to hear. Prydain is Wales seen through a boy's ambition: a country of cantrevs and barrows where the Horned King rides, the Cauldron-Born cannot be killed because they are already dead, and the smith, the weaver and the shepherd know things a hero does not. Lloyd Alexander drew on the Mabinogion for five novels — The Book of Three, The Black Cauldron, The Castle of Llyr, Taran Wanderer and The High King — and added The Foundling, a set of shorter tales filling in the country before Taran was born: how Coll got his pig, how Fflewddur Fflam came by the harp that snaps a string every time he embroiders the truth. It is children's fantasy that refuses the easy version of growing up. The fourth book is a long detour in which Taran learns he is nobody in particular and has to decide what that is worth, and the fifth does not let anyone off. Read the five in order, starting with The Book of Three; The Foundling can come at any point, and is better once you already love the place.