Mary Stewart's Merlin Trilogy is an omnibus edition of the first three novels in Mary Stewart's Arthurian Saga: The Crystal Cave (1970), The Hollow Hills (1973), and The Last Enchantment (1979). The omnibus was published in 1980 by William Morrow and Company. In 1983, Stewart published a fourth instalment in the series: The Wicked Day. HarperCollins republished the omnibus as The Merlin Trilogy in 2004. Source: Wikipedia (en)