Cal's previous books were a big influence on me both when I was a student, and I've continued to heed his advice as I'm early in my career. In his latest book, Deep Work, Cal exhorts the value of deep work -- difficult, mentally taxing and value-producing work -- over what he calls "shallow work", which he categorizes as email, mindless admin, meetings and the like. He argues that by focusing on deep work you'll be happier, more productive, and ultimately advance in your career much faster as well. If this has as big an impact on my life as Cal's earlier books, then it's worth 100x what I paid for it.