Complex sentence: The most important work which has come from this book is "The Miraculous Journey of Mohammed", which tells of the ascension of Muhammad to heaven, and which was composed between 1436 and 1437 (840 in the Islamic calendar).
Split into simpler sentences: The most important work from this book is "The Miraculous Journey of Mohammed", which tells of the ascension of Muhammad to heaven. It was composed between 1436 and 1437 (840 in the Islamic calendar).