Complex sentence: The break-up lasted sixteen years, accompanied by drugs, alcohol, and bizarre behaviour by both parties, such as Snowdon's leaving lists between the pages for her to find, of "things I hate about you".
Split into simpler sentences: The break-up lasted sixteen years, accompanied by drugs, alcohol, and bizarre behaviour by both parties. Snowdon therefore took to leaving lists between the pages for her to find, of "things I hate about you".