To locate a biography do a Browse Subject search in The CAT. Enter the name of the person as the subject. For autobiographies do an Author search.
Unfortunately, ,any people are not famous enough to have entire books devoted to them (or you may not want to read an entire book!) In these cases, consult a biographical dictionary or encyclopedia. These sources provide a brief essay (a paragraph to a few pages) summarizing the individual's major accomplishments. The library has hundreds, if not thousands, of these sources. The ones below will get you started.
For service records see the "Military Records" section of the Genealogy and Family History guide.
The sources below often give minimal information about individuals, but can be useful to verify service, and to place people within their historical context.
The links below are for general sites and those that provide starting points for research.