Complex sentence: Whether James could have managed the details of Ralph's trip through the past and return to the present is problematic; he abandoned the novel in 1900 because the material was becoming too intractable and convoluted.
Split into simpler sentences: Whether James could have managed all the complex details of Ralph's trip through the past and return to the present is a very real question. He broke off the novel in 1900 because the material was becoming too intractable and convoluted.