The book, also known as Darwin's Journal of Researches, is a vivid and exciting travel memoir as well as a detailed scientific field journal covering biology, geology, and anthropology that demonstrates Darwin's keen powers of observation, written at a time when Western Europeans were still discovering and exploring much of the rest of the world. Although Darwin revisited some areas during the expedition, for clarity the chapters of the book are ordered by reference to places and locations rather than chronologically. With hindsight, ideas which Darwin would later develop into his theory of evolution by natural selection are hinted at in his notes and in the book (Summary from Wikipedia).