Complex sentence: Crockett made considerable sums of money from his writing and was a friend and correspondent of R. L. Stevenson, but his later work has been criticised as being over-prolific and feebly sentimental.
Split into simpler sentences: Crockett made considerable sums of money from his writing and was a friend and correspondent of R. L. Stevenson. His later work has been criticised as being over-prolific and feebly sentimental.