Complex sentence: Two further books, a vast philosophical work entitled "Panacea" (running to over 1000 pages in manuscript form) and the novel "Go Back at Once", have also never seen publication.
Split into simpler sentences: Two further books, a vast philosophical work entitled "Panacea" (running to over 1000 pages in manuscript form). This, and the novel, "Go Back At Once" have also never seen publication.