The third novel in Tad Williams's epic fantasy trilogy Memory, Sorrow, and Thorn, To Green Angel Tower concludes the tale set in the fictional world of Osten Ard. The preceding volumes were The Dragonbone Chair (1988) and Stone of Farewell (1990).

When first published in the spring of 1993, the book proved problematic for publisher DAW Books, as it was simply too big to be printed in one volume. The U.S. hardcover was well over 1,000 pages long. The paperback, however, clocked in at 1,600 pages and was thus split into two volumes. In the United Kingdom the two paperback volumes were named Siege and Storm.