Update!
This post originally contained a long introduction about using books as sources. That's been moved to its own post, here.
Information specific to ebooks has been left in this post and I've added links to some shops where you can purchase genealogy ebooks.
There are lots of ebooks for genealogy out there. Many are FREE!!!
I hope this isn't news to you. If it is, you're missing out on a great, usually free, online resource that is pretty simple to use.
[learn about using books as a source, here].
Search Problems
One pitfall specific to ebooks is search accuracy. Ebooks are mainly OCR searched. Occasionally you will find a fairly recent book that is digitized directly from the file, but most genealogy books are older.Depending on the style of text and condition of the book, the accuracy of the OCR results will vary. Although OCR technology is constantly improving, some books will consistently have problems because the text is barely legible to a human eye.
If there is an index, you should manually check it in addition to searching. If a book appears to have OCR issues, see if a table of contents indicates a section you should read.
This completes the advantages, pitfalls, uses, and types of books/ebooks you will generally encounter in genealogy.
Books provide an easy way to find information, but you can't stop there. You need to learn to evaluate sources and test the information and evidence.
Types of books most often digitized (for free) include both histories and abstracted/transcribed records. How-to guides are usually not available for free.
Four Great Sites
So where can you find free digitized books?My favorite source for genealogy books is FamilySearch Books. This is part of FamilySearch.org, and you will find links to digitized books in the catalog, or you can search just digitized books.
Not all the digitized books are available from home. Some of them can only be accessed in a Family History Center. You can still find they exist, though, so you can have a research plan and your research log ready when you get there.
Perhaps my favorite source for digitized books is Google Books.
Not surprisingly, the search function is great. Results will come up in a general Google search, or you can search Google Books directly. Once you find a book, you can then search inside just that book.
Google Books mainly has histories instead of abstracted/transcribed records but also includes books you should use as a tool. An example would be books of laws (such as law digests) so you can perform law research. You may find court cases involving your ancestor, but more likely you will be researching the law for a specific situation.
Internet Archive also has many histories, but their search is not as accurate as Google Books. I always use the Google Books version if the book is available in both, but you may have different results. As a general rule, I don't search Internet Archive directly; I perform a Google search for a book.
I believe of all the suggestions, the Digital Public Library of America (DPLA) is the newest. It isn't just books, and some results may not have digitized images (this is also possible with Google Books).
For the type of professional work I often do, I usually like to search just books because I'm looking for something specific. For personal research, a site with a variety of source types shouldn't be a disadvantage. If you want to learn a bit more about the DPLA, you can read an article by Amy Johnson Crow, CG, here.
Lastly, as a bonus because it's not free from home, is Ancestry.com. You may be able to use Ancestry.com for free at your local library.
Ancestry.com has many digitized books, but it is not always easy to find them. You can browse to see what is available for a location or search the card catalog, but you can't really search just the digitized books.
I occasionally find a digitized book result in my general search, but usually, I have to find the book and search or browse it. Also, Ancestry.com has databases based on books. That means there is not a digital image, just a database. This is basically an abstract of the book so typos or OCR errors can be present on top of the errors created in the original book.
Ancestry.com does have some books as both a database (no images) AND digital images (with or without a database). When this happens, they will have two different names.
Sometimes the database has the name closer to the book's title which leads you to believe this is the best or only version. Usually, the database was on Ancestry.com, first, before digital images became so common. If I find a database-only version, I double check for a digital image, on Ancestry.com and via a Google search.
I can't give you an "in general" type of book you will find from Ancestry.com as I've found all sorts of books but not with any consistency.
Ebooks for Sale
I wanted to provide an update to this post (and this includes affiliate links).Genealogical.com (parent of Genealogical Publishing Company and Clearfield Company) has launched an entire site of genealogy ebooks you can purchase, in your choice of formats. Yes, you have to buy them, but most genealogists have a decent home library. Those that don't are either just getting started or move a lot.
Ebooks mean moving is no longer an issue. In fact, you never need to worry about storage space (other than digital storage space), again! You can find the Genealogical.com Ebook Store, here.
Genealogical.com is a great source for books of records and they also have general genealogy reference (how-to guides, etc.).
If you are looking for more how-to ebooks, paper books, or supplies, check out one of my favorite sources for digital resources, the shop at FamilyTree Magazine.
There are many other sources for digitized genealogy books. You should check for sources for the locations you are most interested in as well as any other specialized research topics. If you have a favorite source for online genealogy books, leave a comment.