You can search the UA Library Catalog for both, print and electronic books that contain primary historical information. Begin with a keyword for your topic. Try combining your topic with additional keywords, such: diary, journal, letters, correspondence, autobiography, map, register, roster, record, primary source, etc. You can also search by Title, Author, or Subject.
Many historical books can be accessed for free using any search engine. These are usually available in PDF format.
Some specific collections of freely available e-books are: