Complex sentence: The More Library is the main library for student use and was opened in 1933 on the ground floor in what were, until then, the Higher Line and Lower Line reading rooms, and are today classrooms.
Split into simpler sentences: The More Library is the main library for student use. It was opened in 1933 on the ground floor in what were, until then, the Higher Line and Lower Line reading rooms, and are today classrooms.