For a sociologist who studied these religions of India only through secondary sources, Weber was very well informed for his time and provided valuable insights, which are still very relevant today.
Unfortunately, "Religion of India", the widely available English translation by Hans H. Gerth and Don Martindale published in 1962 is so full of glaring and elementary errors that it makes for painful reading. (Examples of such elementary errors can be found in David Gellner's book, "The Anthropology of Buddhism and Hinduism: Weberian Themes".) As such anyone who is interested in what Weber had to say about Hinduism and Buddhism has no choice but to turn to the original German.
Fortunately this paperback volume is very affordable so if your university library only holds the English translation, you can get hold of this volume easily.