Since Shirer was a correspondent for CBS Radio in Berlin during Hitler's rise and the book was published in 1960, would it be fair to call his book a primary source?
If you're studying Nazi Germany, that book is pretty solidly a secondary source, and not a very reliable one. It was written after the fact, and based on a collection of Nazi documents, in addition to the author's memories. What exactly counts as a primary or secondary source depends on what question you're studying, though, so if you're studying the way Americans in 1960 thought about Nazi Germany, it's a great primary source