All newly published in book form, Simplex 150 has been compiled by Mary O' Brien, who has been setting the Simplex crossword for more than 20 years. This is her ninth book.

Solving Simplex, the most popular crossword in Ireland, is an integral part of the day for Irish Times readers. It first appeared in the newspaper on 21 May 1951, initially on Mondays, Wednesdays and Fridays. It was immediately popular and the newspaper soon bowed to pressure from readers to publish it in every edition. The format has changed little in the past 55 years, offering today what it always has: a mild degree of mental stimulation, a gentle challenge and a most enjoyable break from the stresses and strains of daily life.