Complex sentence: The New Directions "Poet of the Month" series consisted of thin volumes of either lengthy individual poems or small collections of poems by one author were released on a monthly basis, and a larger "Poet of the Year" volume was issued once annually.
Split into simpler sentences: The New Directions "Poet of the Month" series consisted of thin volumes of either lengthy individual poems or small collections of poems by one author, and were released on a monthly basis. A larger "Poet of the Year" volume was issued once annually.