There are literally hundreds of book sellers online, and the number grows each day. I have found several dealers who specialize in Lincoln and the Civil War, and am pleased to refer you to them.
Chuck Hand
P.O. Box 5
Paris, IL 61944
(217) 463-4555
Email: butch@tigerpaw.com
Web site: http://www.tigerpaw.com/alincoln/
Abraham
Lincoln Book Shop
Prairie ArchivesLocated in Lincoln's own hometown, Prairie Archives features
an outstanding selection of used and rare Lincoln books, pamphlets,
and periodicals. Also to be found is a huge selection of general
used books, prints, posters, records, compact discs, newspapers,
political items, ephemera. . . . I could go on and on. In fact,
about the only thing you can't find at Prairie Archives
are sewing notions and personal health care items. But not to
worry, these supplies can easily be found at the Osco Drugs next
door. A visit to the Springfield Lincoln sites would not be complete
without a visit to this landmark shop, located on the Old State
Capitol Square. Stop in and visit John Paul, and when you meet
Hannah, she loves to get a good scratch behind the ears. (Note:
Hannah is John's dog, not his wife.)
Main Street Fine Books & Manuscripts, Ltd.Operated by Bill and Yolanda Butts, Main Street Fine Books and Manuscripts is located in Historic Galena, Illinois, home of Elihu Washburne and Ulysses S. Grant. A popular tourist destination here in the Midwest, a visit to downtown Galena is like stepping back into time. Main Street is located amongst any number of antique and specialty shops. Those unable to visit in person will find an excellent selection of Lincoln and Civil War material on Main Street's website. Whether in person or online, you will enjoy visiting Main Street Fine Books and Manuscripts!

McGowan Book Company
P.O. Box 4226
Chapel Hill, NC 27515
1-800 -449-8406
Fax: (919) 968-1644
Email: info@McGowanBooks.com
Web site: http://www.mcgowanbooks.com
McGowan Books of Chapel Hill, North Carolina, specializes in
used and rare books relating to the Civil War and Abraham Lincoln.
They recently purchased the private library of Chicago dealer
and collector Ralph G. Newman, which was composed primarily of
both Lincoln and Civil War titles. Their site contains a browsable
list of books within their fields of specialty. One can find a
very nice selection of used books in their fields of specialty,
with a knowledgable and friendly staff.
Hooked on History
Michael J. Fry
Lincoln-Link
1175 D Sanborn Place
Columbus, OH 43229
Email: mfry@cd.pvt.k12.oh.us
Mike is a private dealer who specializes in Lincoln books and pamphlets along with CDVs and other ephemera. He sends out occassional lists via email. With an eye toward personalized service, Mike would also be happy to receive your want list in an effort to fill those open spaces on your bookshelf.
In addition to those dealers listed who sell new as well as used and rare books, there are several site online that sell current titles. A few such purveyors are listed below:
Amazon Books
http://www.amazon.com
One of the largest booksellers in the world Amazon features a catalog of over 2-1/2 million titles. Many new books are offered at discount prices of 20% to 30%. They also provide a search service for out-of-print books.
Barnes and Noble
http://www.barnesandnoble.com
Barnes and Noble opened an internet web site to compete against Amazon for the title of the world's largest online book service. They feature discounts of 20% to 30% on new titles.
Bookfinder
is a great place to start your search for used and new books.
It is a free service that combines the best of many different
book search services. Through entering author, title, and/or keyword,
Bookfinder searches ABE, Amazon, AntiQBook (a Dutch vendor with
an emphasis on European titles), Bibliocity, Alibris, and Powell's
Book Stores.
Based
in Victoria, Ritish Columbia, ABE bills itself as the "World's
Largest Source of Out of Print Material." A sophisticated
search engine allows you to seazrch by author, title, and subject.
Alibris, the successor to Interloc, has recently changed the
way they do business.
Rather than serving as a point
of contact between buyer and dealer, it now serves as a clearinghouse
for the books sold through their service. The buyer contracts
directly with Alibris to purchase the book, rather than the dealer.
While not uniform among all booksellers, it appears that many
dealers who subscribe to this service mark up the price of the
book to pay the 20% premium to the middleman.

Books and Book Collecting offers many resources for the book collector. They have several links to bookseller's searchable databases, as well as references that prove useful to the collector. It is amazing how much information they pack into this site.