These books are fully available online in PDF format and can be downloaded to your own computer.
About three years ago, I had a family history book scanned at the Mesa FamilySearch Library for inclusion in the FamilySearch.org collection. That book has finally appeared. Here is the link:
Overson, Margaret Godfrey Jarvis. George Jarvis and Joseph George De Friez Genealogy. Mesa?, Ariz: M.G. Jarvis Overson, 1957.
By the way, there is a way to copy a permanent link to each of the digitized books if you click on the "Copy Link" link in the menu bar when the book appears.
Now for some perspective. Ancestry.com has a little over 23,000 digitized Stories, Memories and Histories listed in their Card Catalog. Archive.org has about 80,000 genealogy related books in their digitized collections, but not all of them are histories, some are original source documents. Of course, there are a huge number of digitized books in Google Books, but it is virtually impossible to determine how many are fully available without searching through huge lists of returned items. It appears now, that FamilySearch.org has surged ahead of any other source for genealogy specific digitized books.
Look for the Books link under the "Search" menu link at the top of the startup page for FamilySearch.org.
Here is the announcement from FamilySearch.org:
FamilySearch has announced they have reached a milestone in their collection of Family History Books found at FamilySearch.org. More than 100,000 books have now been scanned and published online by the partnership of the Family History Library, Allen County Public Library, Brigham Young University Harold B. Lee Library, Brigham Young University Hawaii Joseph F. Smith Library, Church History Library, Houston Public Library - Clayton Library Center for Genealogical Research, and the Mid-Continent Public Library - Midwest Genealogy Center. Family History Books are available to search and use on the FamilySearch.org website and can be viewed by clicking Search and then clicking Books.
The majority of the online books are family histories, with a smaller portion made up of cemetery records, local and county histories, genealogy magazines and how-to-books, gazetteers, and medieval histories and pedigrees. These valuable resources are viewed by more than 100,000 people a month.This is a significant, I must say, very significant event in the genealogical community.