With a Jack Black “Gulliver’s Travels” vehicle on the front burner, 20th Century Fox is the latest studio to tackle Jonathan Swift’s enduring classic. The novel has already spawned a dozen or so bigscreen and smallscreen projects, including a 1939 Paramount pic and a 1996 NBC miniseries starring Ted Danson.

So, what is it about the 1726 novel that’s so irresistible? Two words: public domain. The property doesn’t cost a thing to option.

Check out any studio development slate and you’ll find a smattering of classic lit adaptations in the works. In addition to the myriad Jane Austen plots being hatched, there are at least two versions of Jules Verne’s “20,000 Leagues Under the Sea” cooking, at Disney and Fox-Scott Free, respectively — not to mention all the Greek classics-based pics in the works.

Public domain law is complicated, but to simplify, books are usually fair game after roughly 95 years. And many books are still well-read long after their copyrights have expired — think Bram Stroker’s “Dracula,” Mary Shelley’s “Frankenstein” and Leo Tolstoy’s “War and Peace.”

But for Hero Pictures’ Fernando Alessandri, who is developing a modern-day take on Alexandre Dumas’ “The Count of Monte Cristo,” saving an upfront book option fee wasn’t the biggest incentive.

“It wasn’t about money for us; it was the richness of the pitch, a very solid story that’s already proven to work about human nature, revenge and forgiveness,” he says. “The fact that it is in the public domain is a bonus.”