NEW YORK (AP) - James Patterson's latest best seller, "The Angel Experiment," is a little different from his usual hits. The novel isn't new; it came out four years ago. Readers aren't picking it up at bookstores, but mostly on the Kindle site at Amazon.com.

And the price is low even for an old release: $0.00.

"I like the notion of introducing people to one book, while promoting the sales of another," says the prolific and mega-selling author (and co-author) of numerous thrillers." His Kindle download is the first book of Patterson's "Maximum Ride" young adult series.

"We've given away thousands of free e-copies," Patterson said. "`Maximum Ride' is big already and we think it could be a lot bigger. That requires getting people to read it."

Patterson is among the biggest brands added to the growing list of free e-book offerings. Over the past few months, top sellers on the Kindle - with downloads in the tens of thousands, authors and publishers say - have included such public domain titles as "Pride and Prejudice" and "The Adventures of Sherlock Holmes," and novels by Jennifer Stevenson and Greg Keyes.

In recent days, the top three Kindle sellers have been free books: Patterson's, Joseph Finder's "Paranoia" and Keyes' "The Briar King."

"There's always going to be someone who wants free things. What we're trying to do is link free with paid," Maja Thomas, senior vice president of digital media at Patterson's publisher, the Hachette Book Group, said. "It's like priming the pump."

"What we like to do is make the first book in a series free, usually a series that has multiple books," said Scott Shannon, publisher of the Del Rey/Spectra imprint at Random House, Inc., which published Keyes' fantasy novel.

Shannon said Del Rey has had especially good luck with Naomi Novik's "Temeraire" fantasy series after offering the first book for free. He said sales for the other Temeraire novels increased by more than 1,000 percent. "It's been stunning," he said.

Publishers and authors have been nervous that the standard cost for electronic editions of new releases, just under $10, will take away sales from the more expensive hardcovers and set an unrealistically low price for the future. They are concerned, but open-minded, about free books, which present a chance and a challenge: Readers may buy other books, or, they may simply seek more free titles.

"It's a huge hot-button topic we've been discussing within our division and at the corporate level," Shannon said. "We have had phenomenal success with using free books to get people to buy others by an author. But in the long term, we have to guard the market. We have to make sure people understand that time and energy goes into writing a book."

"Consumers love free - free is a good price. But the opportunity they present to publishers is to experiment, and I stress experiment," Ellie Hirschhorn, Simon & Schuster's chief digital officer, said.

The dominant e-book seller Amazon.com has been aggressive about keeping prices low, and has given free e-books high visibility by including them on the Kindle best-seller list. A leading rival, Sony, does not include free works among its best sellers, although some free books have popular downloads.

"We do withhold them from the best-seller list, so that it's an accurate reflection of what people are actually buying," says Sony eBook store director Chris Smythe.

In an e-mail statement about free ebooks, Amazon.com spokeswoman Cinthia Portugal, said, "We work hard to provide customers with the best value possible and pass savings on to them whenever possible." Portugal added that Amazon includes free books among its top sellers because the list is "based on customer orders - customers are still ordering these books, they just have a price tag of $0.00."

David Bailey, 56, a systems analyst in Tacoma, Wash., is the kind of customer publishers and authors want to get. He has downloaded free texts by Kelly Link, Scott Sigler and others, but has then purchased other books by those authors, sometimes "just to support them."

One of Bailey's free downloads was Finder's "Paranoia," a thriller first published in 2004. Finder, whose "Vanished" comes out Aug. 18, said he initially saw the free offering as a "no lose" deal since "Paranoia" wasn't selling many copies anyway and sales for his other books, including "Power Play" and "Killer Instinct," have gone up. But, noticing all the free best sellers on the Kindle, he wondered if readers will get used to not paying.

"I get a lot of e-mails from people, saying, `I hadn't even heard of you until I read your free book.' So no question, it does bring in free riders," Finder said. "But I'm also increasingly concerned. There are so many free e-books that basically you could stuff your Kindle or Sony Reader with free books and never have to buy anything."