Complex sentence: For over a year from April 1917, he also appeared alongside Lionel in a stage version of George du Maurier's 1891 novel "Peter Ibbetson"; the play--and particularly the parts played by the two Barrymores--were warmly regarded by the critics.
Split into simpler sentences: For over a year from April 1917, he also appeared alongside Lionel in a stage version of George du Maurier's 1891 novel "Peter Ibbetson". The play--and particularly the parts played by the two Barrymores--were warmly regarded by the critics.