Complex sentence: Their first expedition in 1899 ended tragically, as detailed in the book "Voyage au Trombetas" begun by Henri Coudreau, describing their voyage up the Trombetas tributary of the north bank of the Amazon.
Split into simpler sentences: Their first expedition in 1899 ended tragically, as detailed in the book "Voyage au Trombetas" begun by Henri Coudreau. It describes their voyage up the Trombetas tributary of the north bank of the Amazon.