Complex sentence: Feiffer considers the double-spread illustration of demons late in the book to be a success and one of his favorites, being different from his usual style (which would involve a white background), instead using Gustave Doré's drawings as an inspiration.
Split into simpler sentences: Feiffer considers the double-spread illustration of demons late in the book to be a success and one of his favorites. It differs from his usual style (which would involve a white background), and instead uses Gustave Doré's drawings as an inspiration.