Quite often at cocktail parties or in the first-class cabins of transatlantic flights I find myself engaged in conversations about rare books. The general belief is that if a book is old it must then be rare. Without going into a
lecture on sociolinguistics, it has to be admitted that "old" is relative, and that the term "rare" is too often thrown about carelessly in the world of collectible books.
Books can be collectible without being rare. These would be titles or authors that have resonance with the collector. Fight Club and first editions or signed editions from the Twilight saga are examples of collectible books.
Other books have moved beyond the collectible category and are truly rare. The three-volume first edition of Pride and Prejudice is a great example. It's a classic case of supply vs. demand. The first edition is desirable and scarce. Mathematically expressed, the formula looks like this: D + S = $.
Collectible, rare, and scarce books are just like cars, only with fewer moving parts. By that I mean that much of the same criteria are used to assess them. Physical condition plays a huge part in the valuation. Highlighting, library stamps, crayon drawings, broken bindings, mold, mildew, and coffee stains are the equivalent of a lamp post through the front end of your Ferrari.
Books can be scarce without being rare. Just remember that there are books no one cares about, not even a little bit. They are not significant. They are not a touchstone to history. There might not be very many of them, but so what? A great example of a book that is scarce and valuable is Tamerlane by Edgar Allan Poe. Fifty copies were printed in 1827. This is the book you want to find in that old trunk in the attic, or buy for 50 cents at a garage sale.
The best example of a scarce, rare, significant title that we have on our shelves today is History of the Expedition under the Command of Captains Lewis and Clark. Rebacked, retaining the original boards, complete with the map in very good condition; again, not a bad find if you happen across one in that mythical trunk in the attic.
Our copy of Der Kampfwagen in der heutigen Kriegfuhrung might not look like much, especially if you have trouble reading the Old German font. It is scarce ? only three libraries in the world (https://www.worldcat.org/) hold copies. It is in good condition, complete with the folding map. It is also historically significant.
If you know the reason why Der Kampfwagen is historically significant, be the first to leave the correct answer in a comment below. I'll reward your knowledge with a Powell's treat ? whatever I can grab from the marketing department while they're in a "meeting."