Complex sentence: He was able to devote most of his life to writing this work; after completing it in around 1632 it circulated around interested people in several manuscript copies for almost 80 years before it was first published by Curll in a very inferior form.
Split into simpler sentences: He was able to devote most of his life to writing this work. After he completed it in about 1632 it circulated around interested people in several manuscript copies for almost 80 years before it was first published by Curll in a very inferior form.