The Tombs of Atuan (1970) is the 2nd book in the Earthsea series after A Wizard of Earthsea (1969). 

Not as good, in my opinion.

Too little happened.

Tenar is a young girl taken while still a child to be the high priestess to the “Nameless Ones” at the Tombs of Atuan.

Her existence at the Tombs is a lonely one, deepened by the isolation of being the highest ranking priestess.

Her world is disrupted by the arrival of Ged, the protagonist of A Wizard of Earthsea, who seeks to steal the half of a talisman that is buried in the treasury of the Tombs.

Tenar traps him in the labyrinth under the Tombs, but she then rebels against her teaching and keeps him alive.

Through him she learns more about the outside world, and she begins to question her faith in the Nameless Ones and her place at the Tombs.

I did like that it questioned religion and posed ethical questions back in 1970.