Complex sentence: The book was probably written to please Potter's American fans and its disappointing qualities have been ascribed to Potter's growing disinterest in writing for children, her publisher's expectation of yet another book, and the author's desire exploit the lucrative American market.
Split into simpler sentences: The book was probably written to please Potter's American fans. Its disappointing qualities have been ascribed to her growing disinterest in writing for children, her publisher's expectation of yet another book, and the author's desire to exploit the lucrative American market.