If you ask the average pastor or teacher to recollect their most plentiful keepsakes
  from college or seminary, they will probably miss the obvious. All the textbooks they had
  to buy! Check your pastor or teacher's office or basement and you're sure to find many
  such keepsakes.
  Books are what we learn from and become portable memories. They needn't be acquired in
  formal centers of learning. Most likely they were picked up at the local bookstore or
  through the mail. Many have been treasured possessions for years. How many Lutherans still
  have their first Catechism from age 14 or earlier?
  Dr. Martin Luther was a prolific writer. Yet he also was an extensive reader. Note what
  he said in 1524:
  
    "My advice is not to huddle together indiscriminately all sorts of books and to
    look only to their number and quantity. I would make a selection of books. There is no
    need of collecting the commentaries of all jurists, the sentences of all theologians, the
    questions of all philosophers, and the sermons of all monks. In fact, I would throw out
    such dung and furnish my library with the right sort of books, consulting with scholars as
    to my choice."
    (Ewald M. Plass, Compiler, "What Luther Says: An Anthology", Vol. 1, Concordia
    Publishing House, St. Louis, 1959, pp. 110-111.)
  
  Today's Christian usually has at least one book in their possession, the Holy
  Scriptures. Chances are they have many more besides. Dr. Luther noted that readers need to
  be discriminating in what books they acquire. That advice is good for today as well. Then
  as now the volume of books on any given subject can make a careful selection difficult. We
  find ourselves asking others for their advice so as not to err.
  Yet still, we acquire more than we probably need. Or we pick up materials by mistake
  that we later regret. Since the "Luther Quest
  Discussion Group" went online, there have been many occasions where participants
  have recommended or asked about various books. Many of these books are rather distinctive
  and aimed at a limited audience. It isn't always easy to find a local bookstore that has
  them in stock. Even the local Lutheran bookstore could have a difficult time. And if the
  book is out of print, you are guaranteed a long wait that could prove fruitless. What do
  you do then?
  With the advent of the Internet, the sources for buying and selling both old and new
  books are just a mouse click away. Also, you are not limited to dealing with professional
  booksellers. Individual book owners are also able to list their wares for the shopper to
  find. With various Internet search engines linked to these websites, it becomes even
  easier with a higher level of success. There are three websites we would like to recommend
  for your use in hunting for good books. Ive found them to be quite helpful,
  especially with locating out-of-print books.
  Two of the websites are search engines that search other websites that are distinctly
  composed of booksellers, professional and individual. While both of them overlap in most
  of the booksellers they search, they differ enough to warrant your use in any particular
  search. Both of these search engines let you look for new or used books. The third website
  is where individual and professional booksellers can list their books. This site is
  intended for those with books they no longer need and wish to sell. Plus, we think it
  would be convenient for readers of Reclaim News, Luther Quest (or other discussion group)
  participants, and other Lutherans to have a common locale where they can list books for
  sale that other Lutherans may be interested in.
  The first website is www.BookFinder.com. This
  search engine currently searches 9 of the largest and most popular new book dealers and 10
  of the largest used book websites in the world. You are basically searching about
  20,000,000 books (not a typo) when you use BookFinder. The second website is www.AddALL.com. They have two distinct search features,
  new and used. The new books search goes through about 35 of the largest booksellers. The
  used book search will process the top 8, most of them duplicating the selection from
  BookFinder. However, the overlap is not total, and thus you are advised to use both
  companies to increase your chances of success. Both of these sites have proved very
  helpful for me when trying to find those old Concordia Publishing House items from many
  years ago.
  For those with their own books to sell, we would like to
  recommend www.Bookopoly.com. They currently have
  over 700,000 listings, with over 4,600 listed under "Non-fiction > Religion."
  Listing your books on Bookopoly is free, with a low commission of 5% on items you sell. A
  large competitor to Bookopoly charges three times that amount.
  Bookopoly has over 120 individual subject classifications under 11 main subject
  categories. Anyone can search through the Bookopoly listings. Membership is free and both
  sellers and buyers must join to engage in any transactions. This protects both parties.
  Bookopoly is listed in many of the main Internet search engines.
  You can list as many books as you like, describing their condition, sale price, etc.,
  in a very easy format. An added feature is the ability to create your own Book Web, or
  webpage, within the Bookopoly site. The address to your Book Web can be shared with
  friends and family to show them what you have for sale. The best thing about Book Web is
  anyone can use it. You dont need to be a webpage designer or programmer to put
  together what you want. Any changes you need to make are also easy to do. Editing of items
  youve listed can be done at any time.
  You, the seller, set the sale price of the books. Its advisable to use search
  engines like BookFinder and AddALL, listed above, to get an idea of what your book is
  worth before setting your price. Shipping and handling are also yours to determine.
  Bookopoly requires all pricing to be in U.S. Dollars, and recommends shipping costs for
  U.S. destinations by U.S. Media Mail. Naturally, you can list alternative methods in case
  buyers desire other delivery services.
  Another nice feature on Bookopoly is a section of Want Ads. You can list for free any
  book youre looking for in the Want Ads, which happen to be scanned by various
  booksellers. Plus, you can always scan the Want Ads to see if someone wants a title that
  you own and would be willing to sell.
  If you have any questions on what youre doing, they have an extensive Help
  section. If that doesnt contain the answer youre looking for, you can email
  your question to Bookopoly, and theyll respond pretty quickly. Thats one key
  area I researched before making this recommendation. A service is only as good as their
  support level. And Bookopoly has a very high support level.
  Books are key resources for us to use as Christians in general and Lutherans in
  particular. Being able to obtain the titles you want is key. With the aid of the websites
  listed above, you will have some adequate resources to both buy and sell your books.
  Keeping Luthers advice in mind, you are now equipped to furnish your library with
  discriminating choices.