IBM’s official biography of Hollerith contains detailed information about his early life and his later career.
You can also read the Census Bureau’s biography of Hollerith, which is shorter but less biased.
Read “An Electric Tabulating System,” written by Hollerith in 1889. The article lays out a detailed description of the problems facing the Census, and how Hollerith’s tabulating system would streamline the process.
Check out the Punched Cards exhibit from the Computer History Museum. It covers punch cards generally, beginning with Herman Hollerith and continuing through the 1950s. It also includes information on the uses of punch cards, from the Census to scientific and military applications.
IEEE: “Hollerith Punched Card System Development,” Friedrich W. Kistermann: This article focuses on the mechanics and intricacies of the Hollerith systems as they evolved over time, and also covers Hollerith’s attempts to comply with the the changing desires of his customers.
The Universal History of Computing, Georges Ifrah, pgs. 180-183