A bestselling book on Area 51 is so controversial that it has shocked even its sources with an outrageous claim that the infamous Roswell, N.M., UFO crash of 1947 was really caused by Soviet leader Joseph Stalin and one of the most notorious Nazi criminals.

A group of retired test pilots, engineers and military personnel from the fabled Nevada military installation, who played a crucial role in investigative journalist Annie Jacobsen's new book "Area 51: An Uncensored History of America's Top Secret Military Base" (Little, Brown and Co.), are reportedly unhappy about the writer's shocking conclusion.

"It caught us completely by surprise -- we were blindsided," said T.D. Barnes, a former electronics, radar and communications expert who first came to work at Area 51 in 1968.

While the U.S. government still doesn't confirm the existence of Area 51, many say that Cold War technology -- including the U2 and A-12 spy planes and stealth aircraft -- were routinely tested at this abandoned bombing range nearly 100 miles north of Las Vegas during the 1950s and 60s.

For decades, rumors spread around the area that the military was testing captured alien spacecraft as well as examining the wreckage and remains of extraterrestrials that had crashed outside of Roswell in 1947.

Jacobsen wrote her book to reveal the various secret projects that took place at Area 51, also referred to as Groom Lake, and interviewed a group of former Area 51 personnel, called Roadrunners Internationale, that included Barnes, the president of the Roadrunners.

Despite the true military aircraft testing that went on at Area 51, the one story that has persisted for decades -- and which is enjoying most of the attention from Jacobsen's book -- is the Roswell UFO story.

For more than 60 years, the most fabled UFO legend of all time has been argued and dissected as those on both sides of the issue have tried to identify the source of the object that crashed outside of Roswell.

Until now, theories ranging from alien spacecraft to weather balloon to anti-Soviet Union spy program have been bandied about.

But Jacobsen adds a blockbuster new dimension to the whole picture: Was the Roswell UFO really a Soviet-built circular craft that contained a "crew" of Nazi-based, surgically-altered youngsters built for the purpose of causing hysteria in America?

An unnamed source told Jacobsen the story of how ex-Soviet leader Josef Stalin recruited ex-Nazi Josef Mengele to be part of a scheme where a "UFO with aliens" was created to scare Americans.

According to the tale, Mengele -- the infamous Nazi "angel of death" who experimented on children at concentration camps -- surgically altered a group of youngsters to look like aliens.

When the remote-controlled Soviet-built craft -- and its pseudo ET crew -- crashed in New Mexico, the legend of Roswell was born. The "alien spaceship" and its otherworldly occupants eventually found their way to Area 51 in Nevada for examination. Jacobsen's unnamed source -- an engineer who worked for defense contractor EG&G -- says he examined the Roswell craft and body remains when they arrived at Area 51 in 1951.

But did all of this really happen? Barnes, an ex-Area 51 employee, says he and other Roadrunner Internationale colleagues were upset when they read about the Nazi-Soviet connection to the fabled base. He claims it never happened and shouldn't have been included in Jacobsen's book.

"Everybody's up in arms over the book -- it's got its good points, but the last chapter just destroys what would've been a good book," Barnes told AOL Weird News.

"We're the group that worked at Groom Lake back in the 1950s and 60s," he explained. "We worked on the U2 program and then the A12 [a CIA project that lead to the supersonic SR-71 spy plane]. Our group bonded so closely because of the work that we did, and we've stayed a family all these years. We even had reunions for over 40 years, but they were all secret."

Everything was so secretive at Area 51, Barnes admits, they never talked about it outside of work.

"You really didn't refer to it much. No one knew that it existed, like at home, our wives didn't know where we were working or what we were doing, so it just really didn't have a name."

Barnes says that he and other members of the Roadrunners Internationale felt betrayed when Jacobsen's book came out.

"That's been a real dilemma for us. We originally talked with her for the book because it was an opportunity for us to get our stories told once and for all for the sake of history, our friends and our families.

"But when she added that final chapter, that just totally destroyed the purpose of us talking and being in the book because all the focus is on that last chapter."

But Jacobsen approaches all of this from a purely journalistic attitude.

"I absolutely 100% stand by everything in my book. If others want to disagree with it, that's really their business," she told AOL Weird News.

Jacobsen didn't feel it necessary to let Barnes or anyone else know about the part of her book that speculates the Nazi-Soviet connection to the Roswell UFO crash and the reported subsequent examination of the "UFO" and "alien bodies" at Area 51.

"For starters, journalists don't share their information with their sources prior to publication. That's a standard rule," she said. "So I'm following journalistic tradition."

"What others think of my book can't matter to me in terms of being a journalist," she added.

According to Jacobsen, she's "received overwhelming support from the men in my book and only three notes of discouragement." So it doesn't appear that a lot of the former Area 51 personnel have actually objected to her inclusion of the Nazi-Soviet material.

Yet, Barnes gives a different impression.

"I initially skimmed through it and just went into shock when I saw what was added to it," he said. "I had quite a few words with Annie over it and I told her I would support the good stuff but not the other stuff, so we finally agreed to disagree."

The main part of the problem in this he-said-she-said issue has to do with the controversy itself and the timeline involved.

Whether the UFO that crashed in Roswell was otherworldly or Soviet-based, the date is not in dispute: it happened in early July 1947.

And yet, Barnes, who first arrived at the top secret Nevada base in 1968, insists that nothing described by Jacobsen or her source that allegedly took place there in 1951 was true. And he maintains that the inclusion of the Nazi-Soviet allegation detracts from the true material in the rest of the book.

"She warped the history to fit her theme," according to Barnes. "I'm not telling people not to buy the book -- I'm just asking people to not read the last chapter."

So who's right here? On the surface of it all, it seems that, if you work at a top secret facility, no matter what kind of security clearance you have, does that automatically make you privy to everything else going on there? Probably not, especially if there are many programs and you're not working on them all.

Also, if something allegedly happened at Area 51 in 1951, 17 years before Barnes started working there, would he have a need-to-know about all previous secret activities that took place at the location?

These are important questions to consider if you're trying to grasp what really happened at Area 51 with regard to a flying disc and alien-type bodies.

"First of all, I would never take the opinion of anyone who wasn't there and consider that journalism, because that's called speculation," said Jacobsen.

"If you're asking me if I disagree with others who say it didn't happen, the answer would be yes; if you're asking if I wish I hadn't put it in the book, the answer is no; if you're asking if I think others are entitled to their opinion, the answer is yes," she said.

"When certain individuals show up at Area 51 in 1968, how could they possibly speak to a program that took place in 1951?"