I'm starting a physics PhD program in the fall. I asked a current student what textbooks are used, and was surprised that the textbook for electrodynamics was not Jackson. I got the impression that Jackson was the standard. E.g., My undergraduate institution (a top physics school) uses Jackson as a graduate E&M textbook for their grad program. I've heard the rumors about how hard and tedious the problems are, but I was actually kind of excited to have that experience... Is it recommended to self-study Jackson over the summer? Is Zangwill fine and Jackson better served as a reference book?