Books either have ISBNs or they don't. A simple distinction, but a distinction that has many implications to the beginning book collector or investor.
Book investors can focus on any number of niches, but for the beginner there are basically two types of book to search for when buying and selling. There are subjects, there are genres, there are authors, there are formats-- but in the end there are two major categories: books with ISBNs and books that are either too old or too obscure to have been assigned an ISBN.
ISBNs make book collection, organization, and investment far simpler, and for the beginner this is where I would start. The ISBN uniquely identifies a printing and a format of the work, and makes that work extremely simple to compare prices on and to purchase, and later to sell.
Searching without an ISBN can be very difficult. Without a copy or without good pictures you need far more information than you do with ISBNs. You need to know the year, you need to know the publisher, you need to know the edition, and really you need photos to be positive that what you are buying is what you are intending to buy. Books without ISBNs are generally best purchased in person, and so are generally sold by people who know what they are, and the chances of finding underpriced options is relatively low.
ISBNs give the searcher a vast array of tools and websites to compare dozens of online booksellers and marketplaces to check for availability and the best price. But searching by ISBN has a further advantage in that, especially in valuable books, there is a an incentive for sellers with an incorrect edition to sell their book as the more valuable edition. For example, if you search for Richard Bachman "Rage" (Stephen King's pseudonymous book) on Amazon, you can search by ISBN yet still find books without the correct ISBN in the listings. This is because the prices are so high, and as you go through the offers of the expensive editions, you will see some notes will say the book has a different year or a description that says it's not the same ISBN or something like that. How is this an advantage?
It is an advantage in two ways-- because in this particular instance there are two valuable paperback editions of this book. At this time, one is in the range of $600 and one is in the range of $1,000. So a book that is incorrectly listed may still be quite valuable, and yet be the incorrect book. And these books are probably too expensive for this tactic, but there are times when you will want to order a book that you know is incorrectly listed. When the prices are maybe 10% of what we're looking at here, if you know a book is valuable but you know that that book is in the wrong listing area, you can often buy it and get it for free because it is listed with an incorrect ISBN.
When you receive it youu can tell the seller that this is not the book you ordered, this is not the correct ISBN. Tell them that you need the correct ISBN, and they will generally (on books under say $30) tell you to just keep the book. If it's $50 or more, the returns generally do make sense for them to follow through on, but you can see that there are opportunities in ISBNs that may not exist in other types of books. Because you have a definite number that you are comparing to what you receive, and there's no back and forth on whether it's the right or wrong book.
The other advantage to this situation of expensive book listings attracting incorrect hangers-on is that they can drive down the prices of the correct listings. So someone may list a book that is not the correct edition, but list it in an expensive edition's listings, and the automatic price adjustments from larger booksellers will adjust their prices down, making everything a better value. This can hurt you when you are selling, but when you are selling a valuable book, there are other things you can do, such as reporting incorrect listings. This can be done on the page feedback form of the offer listing page. They will ask for the links to that offer listing and what you think about what makes it inaccurate, and you can let them know there about the error. Or as we discussed elsewhere, you can simply purchase the mistaken listing, sometimes for free.
Some of these things you need to know when investing in non-ISBN books as well, but in the initial short-term sticking to books with barcodes is definitely a way to reduce your uncertainty and get into collecting. ISBNs make selling muck less risky. If you have other techniques, share them with us by email at comments@bookbuys.com. Our comments are moderated and added to the piece.