Ursula K. Le Guin wrote A Wizard of Earthsea in 1968 - a book that was to become one of my favourite books in childhood. To my surprise, the writing is so strong that it's remained a favourite of mine throughout my life, and I've read it multiple times. The Tombs of Atuan is the sequel, although the book belongs more to Arha (also called "Tenar") than Sparrowhawk (the wizard of the previous title). Arha is being raised to be a priestess to the Nameless Ones on the isle of Atuan, and a good portion of the book is about her upbringing and training. It isn't until page 64 of a 163 page book that Arha first encounters Sparrowhawk (and immediately locks him up).
Like its predecessor, the book is a coming-of-age tale. That and a shared setting in Earthsea is pretty much the end of the similarities to the previous book: this one has a darker and more barren feel to it, and relies less on magic. Both our heroes are prisoners: Sparrowhawk in fact, but Arha is bound by tradition and a lifetime of having known nothing else.
I've never liked this one as much as A Wizard of Earthsea: it's bleak, and constrained to the religious compound Arha lives in (and - even more grim - the unlit labyrinth underneath it). But it still reads well, and is a story about the choices we make with our lives: I've probably read it five times so far.