"Herman Forgotten Giant of Information Processing" by Geoffrey D. Austrian is a thoroughly enjoyable and well-written biography of this quintessential pioneer in the data processing field. Austrian does a fine job of developing Hollerith's character as well as telling the story of his accomplishments, while masterfully blending in the history of the computer industry (up until 1982). A definitive, well-documented biography, sure to please both the casual reader as well as the avid history buff.
Read this for background info on Herman Hollerith – I'm giving a talk next month and found Hollerith's story to be fascinating. The book itself is pretty spotty – the narrative fades in and out, there are several areas where the author didn't find what he was looking for and just goes with "well, he probably just did [x]" instead of doing more research. That said, it's a worthwhile account of a critical figure in computing history – glad I read it, even if it wasn't as good as I'd hoped.