Monographs are single-subject books for an academic audience. Books are almost always more focused than reference sources and academic books are even more narrowly scoped than trade books and other mass market publications. A broad understanding of the scope of books is important as you approach any research topic. Student projects often start with a reference source and then incorporate books and more narrowly focused material as the research progresses.
In History 300 you will use books as primary sources and secondary sources depending on the type of book it is. A book entitled The Correspondence and Public Papers of John Jay gives clues you in on the fact that it's contents include letters and possibly diaries and more as direct evidence regarding the life of John Jay.
Google can also be very useful for biographical information. However, it is important to Google WISELY. Remember the ABCs of website evaluation: authority, bias, and currency. If you are not sure if a website is legitmate or cite-able, just ask a librarian!
Did your person create or found an organization? Perhaps that organization has a page dedicated to that person and their history, like the Red Cross does for Clara Barton.
Museums can also be great places to go, even if your person is not an artist. Consider the African American History Museum or the Smithsonian. City museums like the Museum of the City of New York can also be useful, as can "niche" museums like National Cowgirl Museum and Hall of Fame.