As we enter the second decade of the 21st century, ecommerce has expanded to the point that “ecommerce for the masses” has become a tantalizing business opportunity for many of us, both those hoping for a second career and those just hoping to make a few extra dollars on the side while clearing out their basements. However, if you take the next step and move onto a site like eBay.com to sell your books, you’ll quickly discover that roughly a million other people have already had the same idea. And many of them are already selling your books.

So, it’s time to take a step back again and consider what sorts of books are worth selling online. For those reluctant to take the plunge into more strictly regulated environments like the Amazon Marketplace, eBay is easy to use, and still pretty cheap; the “Buy It Now” option is the most popular for listing books online, and you can do that for roughly a nickel per book for a week-length listing. At the moment, eBay also throws in the first five listings of the month for free.

There are four things to consider when selling on eBay: your reputation as a seller (not much you can do about that just yet), the professional appearance of your auction pages, the choice of a good price that balances profitability for you with appeal to the bidder/buyer, and the choice of which books to put up online in the first place. In this article I’m going to concentrate on just the fourth of these.

Essentially, the guidelines for selling books online are more or less the same as those for selling used books in a conventional physical store, with the added bonuses thrown in that books with limited appeal in one region are often more profitable in another, and that on the Internet it’s much more likely you’ll find someone willing to pay considerable money for a vintage edition that’s, through great luck, held together in very good shape.

Fiction Doesn’t Sell – Well, it can, but only in certain circumstances, and not normally for very much money. The bestselling paperbacks of last year (or five years ago) are almost never going to be of any significant value in the secondhand market. On sites like eBay and Amazon Marketplace, you can regularly find them selling for a dollar each, sold by professional used-book merchants whose economies of scale and paper-thin margins allow them to scrape a little bit out of the shipping and handling fees for their profits.

Non-Fiction Might Sell – Go for books that hold their value and continue to attract audiences over a long time. Histories on popular subjects (in America, the Civil War), for example, can continue to attract readers decades after their first publication. In general, the more esoteric the subject, the more quickly a book’s value will depreciate; my copy of Hans Blix’s bestselling analysis of his experiences with the Iraq War, for example, used to be a hot item in bookstores but is very quickly dwindling into utter insignificance, except in the minds of certain military historians and strategic analysts. Incidentally, pay close attention to one non-fiction category in particular:

Old Textbooks Never Sell – Forget about it. A ten-year-old previous edition of a currently used textbook is going to have no demand for anyone whatsoever. The just-out-of-date edition might attract an adventurous student who’s willing to gamble that most of the material is still identical. But beyond that, who wants to buy an old college textbook? Students are virtually the only ones snatching them up in the first place, when they’re brand new. The only plausible exception to this is if you hang onto a textbook for at least fifty years or so, until the information in it becomes so quaintly ridiculous that someone with an interest in the history of education starts to find it intriguing.

Anything Special? – Books that are hard to get are worth more (this is a basic law of economics). Consequently, books that have some special added value are going to be both more visible to prowling potential purchasers, and also more profitable (since you can stick them with a higher price). A first edition of a subsequently popular and reprinted book, for example. Or vintage publications that are a century old but still intact. Or printings where people have spotted errors and thus jacked up the going rate for increasingly scarce copies. (Important caution: hardcovers need to have their intact jackets. If they don’t, they’ll still sell, but their price can drop drastically.) Of course, these sorts of books are the hardest to part with, for the same reason. But they can give you the biggest payoffs.

Selling books online is yet another one of the virtually endless list of supplementary income schemes for which a disclaimer that “you’ll never get rich doing this” is obligatory. Nevertheless, selecting the right books to sell, and the right ones to pulp or at least put back in a storage box, can help you change selling books from a depressing exercise in futility into a more exciting and successful enterprise.