Complex sentence: Biographer Reynolds, however, writes that Hemingway was not involved in the battles described; because his previous novel, "The Sun Also Rises", was written as a "roman à clef", readers assumed "A Farewell to Arms" to be autobiographical.
Split into simpler sentences: Biographer Reynolds, however, writes that Hemingway was not involved in the battles described. Because his previous novel, "The Sun Also Rises", had been written as a "roman à clef", readers assumed "A Farewell to Arms" to be autobiographical.