Complex sentence: He single-handedly built a barn in the Catskill Mountains using the methods and tools of the 18th-century timber framers; and currently, he is working on his eighth book, "A Square Peg".
Split into simpler sentences: He single-handedly built a barn in the Catskill Mountains using the methods and tools of the 18th-century timber framers. He wrote his eighth book, "A Square Peg".