Which author wrote the 'Memory, Sorrow, and Thorn' trilogy?

Tad Williams wrote the Memory, Sorrow, and Thorn trilogy.

The epic fantasy series is set on the fictional continent of Osten Ard and follows Simon, who begins as a kitchen servant at Hayholt Castle. Political conflict, ancient peoples, magical swords, and a supernatural threat gradually draw him into a struggle affecting the whole continent.

The trilogy consists of The Dragonbone Chair, published in 1988; Stone of Farewell, published in 1990; and To Green Angel Tower, published in 1993. The third novel was so long that some editions divided it into two paperback volumes, which can sometimes make readers think the series contains four original novels.

Williams’s trilogy is also notable for its influence on later fantasy. George R. R. Martin has cited Memory, Sorrow, and Thorn as an influence on A Song of Ice and Fire, while Christopher Paolini has named it as an important influence on The Inheritance Cycle. Later stories expanded Osten Ard through The Last King of Osten Ard and related novels, but those works do not change the authorship of the original trilogy.