There are a wide variety of resources online. Some you will have to subscribe to and other are free. Whatever the outcome, they are all great investments to look into! Individuals, local genealogical societies, libraries, and large commercial organizations are digitizing books that contain genealogical information and placing them on the internet. I have found that looking for books on Ebay as well is a great resource. As I have also found family bibles, photos and information sold there as well!
Some of the widely and common used examples are listed below… take a look!!
GoogleBooks is an easy-to-use source of online books. Digitized books in the public domain on GoogleBooks are fully viewable. For publications still in copyright, only a limited view of the contents is available.
When you click on a link for a book that’s available in “limited” “snippet” view you’ll see on the left side of the GoogleBooks webpage a “Find in a library” link. The link goes to WorldCat, an index to the world’s largest network of library catalogs.
Brigham Young University (BYU) Family History Archive is a collection of thousands of published family history materials. There are several ways to search the Family History Archive, but the “Advanced Search” option allows exact phrase searches.
Hathi Trust Digital Library is a partnership of academic and research institutions. Several search options and full text display of many out of copyright or governmental publications are offered.
Internet Archive is a non-profit library of millions of free books, movies, software, music, websites, and more. The “American Libraries” collection lists more than 40,000 entries under subject “genealogy.”
The Making of America at the University of Michigan is a digital library of more than 12,000 nineteenth-century historical books. It is easily searched for names and places.