The publication of a third book came sometime after 23 BC. Its content shows the poet beginning to move beyond simple love themes, as some poems (e.g. III.5) use "Amor" merely as a starting point for other topics. The book also shows the poet growing tired of the demanding yet fickle Cynthia, and implies a bitter end to their torrid love affair. Book IV, published sometime after 16 BC, displays more of the poet's ambitious agenda, and includes several aetiological poems explaining the origin of various Roman rites and landmarks.