My goal is to publish new posts twice a week — Mondays and Thursdays. However, if you don’t see a new post on Thursday, it’s because I was too busy, so please look for a new one the following Monday.

This is a guest post by Adam Weinberger of RareBookBuyer.com, a New York City book dealer with over thirty years’ experience. Please feel free to contact him with your questions about old and rare books.

If you’re like me, you probably have a relative with an attic full of dusty old books. Some of them may be one hundred years old or more. You’ve probably also asked yourself: are those old books valuable? Could you have a hidden treasure, like the people on Antiques Roadshow?

The answer isn’t always obvious. Many old and rare books aren’t inherently valuable. But there are a number of factors you can look at to help you decide whether or not your old book is worth something.

The first factor is rarity: how many other copies of your book are out there? The more rare it is, the more valuable it’s likely to be. It may surprise you, but most books from the 19th century are not very rare—especially bibles and other religious texts. Tens of thousands of copies still exist. Books printed before 1800 have a better chance of being valuable. First editions of a book tend to be rarer and more valuable than subsequent editions. And any kind of unique material—manuscripts, journals, original artwork—is worthy of study by a professional dealer.

The next factor to look at is importance. Was your book influential, groundbreaking, or scandalous? Did it change the course of literature, science, or history? Those are the kinds of books that collectors and dealers are usually interested in.

If you’ve concluded that you have a rare and important book, you next want to look at condition. Is your book in good shape? Just because it looks better than you will in 150 years, don’t assume the answer is yes! Condition can make a big difference in value: The book’s binding should be strong and original. The paper should clean and unspotted. None of the pages should be missing.

Ok, let’s say your book is rare, important, and in good shape. Next you want to know where it came from. That’s called provenance. An interesting provenance can often increase a book’s value. Who owned the book before you? Look for inscriptions or bookplates (an owner’s sticker). Maybe someone important owned the book in the past. Or perhaps it was part of a famous collection. Or it was inscribed to someone close to the author. All of those are examples of interesting — and potentially valuable — provenances.

The last factor to understand is desirability. This one is hard to pin down. It basically means, will someone out there want to buy your book? In some ways, desirability is a combination of the other factors: collectors often look for a combination of rarity, importance, condition and provenance. But it’s possible to have an ancient first edition in pristine condition that no one wants to buy. In that case the book is most valuable—to you!

If you think you have a valuable book, speak to an experienced book dealer. RareBookBuyer is happy to offer free appraisals of your old or rare books. You can contact us by email, webuyrarebooks@gmail.com, or call us at 646.469.1851.

We just decided to add a new show to our schedule, the NYC Big Flea Market. The new promoters, D’Amore Promotions, will be using the same Pier 94 that is used by USA Antique Shows for their November and March shows. This one will be substantially different, with an entirely new cast of dealers. Click here for more information. It should be good, so I’m really looking forward to it.

Click here to view our new website and look around. We always strive to offer the finest objects for sale on our website and at every show. There are many items for sale, sold items with prices and free lessons about glass and lamps.