You find a first edition of “Angela’s Ashes” in with donated books.

Eureka! You think. It’s worth a fortune.

But antique book dealer John Kehoe of Norwalk will tell you that not only is it not worth thousands, it’s not worth even $1.

Kehoe shared a lot of other lessons about what makes a book valuable when he talked to the Friends of Connecticut Libraries at the Fall Conference Nov. 14 at Central Connecticut State University.

The most important thing is the condition of the book.

“Condition is to rare books what location is to real estate,” he said. “Collectors want a perfect copy.” A perfect “Electric Kool-Aid Acid Test” will sell for $750 but a bad one you can’t even give away. Three things that used to drive book values were scarcity, content and appearance. Now appearance is the most important.

“The money is in the dust jacket,” Kehoe said. A book with a dust jacket in pristine shape can be worth 95% more. There is only one known copy of Theodore Dreiser’s “Sister Carrie” with a dust jacket and it is worth $100,000, he said.

“Take care of those dust jackets!” Kehoe said. If a dust jacket is starting to chip, you might get a few dollars more for the book if you put it in a plastic cover.

It’s even harder to find children’s books in good condition. A pristine copy of “Make Way for Ducklings” could sell for $12,000, he said. And very rare is a pre-1960s book with a dust jacket.

He did find one valuable book in the 30 or so that Friends brought to him – one by Charles Darwin. “Any copy of Darwin before 1900 sells,” he said.

One of the most important things you can do at sales is price items appropriately, Kehoe said.

“You can’t run a sale with overpriced books. Buyers are too smart.” A successful sale has little left at the end, he said.

People who try to find what a book is worth by looking it up on the Internet often get the wrong idea. Dealers will put up the price they would like to get for a book, not what it is actually worth.

“What you see are the unsold books,” Kehoe said. “A first edition of ‘Valley of the Dolls’ will sell for $100. People who list it higher won’t sell it.”

You can pay to get access to a site such as Rare Book Hub, which gives the actual selling price of rare books. And the site ABAA.org will show you what professional book sellers are asking for rare books.

“If you have a really good book, price it so it will sell,” he said. “If you price it too high you won’t get it. The important thing is to just get more than you paid for it.” And remember, you got a book as a donation.

A few other tips:

• Don’t use stickers on books because they can damage the dust jackets.
  
• Don’t stock unsaleable books such as “The DaVinci Code” or “A Day in the Life of America.” (Anyone who wants to read them already has.) “The idea of throwing out a book is not that bad,” Kehoe said.
  
• Don’t waste time alphabetizing fiction because it has no impact on sales.
  

The way to get better at pricing valuable books is just like anything else – practice. Set prices and see if books sell for what you ask. A few books on book collecting include “The ABC for Book Collectors” by John Carter and “Among the Gently Mad” by Nicholas Basbanes.

Signed books can be more valuable unless it’s an author known for signing easily. Even if the signature includes a note to someone, that wouldn’t hurt the price.

Who collects rare and antique books? Kehoe said he doesn’t know because it really isn’t a good investment. Books that were valuable 100 years ago often are no longer worth anything.

“Some people collect books because they have a socially acceptable form of OCD,” he guessed.

Kehoe said he got into book selling by accident, just wandering into second-hand bookstores and asking questions. When he found it more interesting than his job at the time – industrial construction management – he made it his career.

He used to pick up books at library book sales but said things are changing. Libraries have gotten better at pulling out valuable books before dealers such as him can find them. And some people go through sales with scanners, picking anything valuable.

Kehoe recommended not consigning books to an auction house because they generally take 25% of a sale and make you wait 90 days for the money. And dealers don’t like to buy at auction, so you’ll end up losing a lot of money.