How to spot a fake: Rare books

According to CNBC "Treasure Detectives" art forgery expert Curtis Dowling, rare books are especially valuable collectors' items. They are also among the most frequently faked, and hardest to detect.

Fakers ply their trade by replicating the same sensations that anyone would perceive when walking into a used bookstore. It's one thing to make a book simply look old and weathered, a feat that can be accomplished with a little paint and an inscription dated back a century and a half. But it's necessary to fool all of the senses, especially touch and smell, to make the experienced collector accept a faked book as the genuine article.

"If this book smells like it's been in a church for 150 years, and it feels like it's old and weathered, then all of a sudden, all of your senses are telling you this is an ancient book," Dowling said. "Then you thumb through it, and there's signs of age and wearing where the oil from peoples' fingers over the years have been touching the pages."

Getty Images

People browse through books at the New York Antiquarian Book Fair.

Still, he said, fakers can achieve the look and smell of an old book with walnut oil.

So how does a collector avoid becoming a victim? According to Dowling, it's all a matter of experience.

"Fakers over-age," he said. "You need to look closely and see if it's real signs of age, real signs of wear, real signs of fading. … You just need to handle a lot of books and you need to smell a lot of books. Only then are you going to be able to tell if a book is old or whether it's new."