Complex sentence: Harrison was fascinated with Olber's Paradox (the night sky is dark despite the vast number of stars in the universe), and published in 1987 an entire book, "Darkness at Night", mulling over the Paradox and its rich history.
Split into simpler sentences: Harrison was fascinated with Olber's Paradox (the night sky is dark despite the vast number of stars in the universe). In 1987 he published a book, "Darkness at Night", mulling over the Paradox and its rich history.