Salt Lake City -- At the "Crossroads of the West" gun show here last weekend, weapons dealers sold semi- automatic rifles and custom-made pistols, and ammunition wholesalers unloaded bullets by the case. But perhaps the most fearsome weapon for sale in the cavernous, crowded exposition center was a book.
Next to the Indian handicraft booth, Timothy W. Tobiason was selling printed and CD copies of his book, "Scientific Principles of Improvised Warfare and Home Defense Volume 6-1: Advanced Biological Weapons Design and Manufacture," a germ-warfare cookbook that bioterrorism experts say is accurate enough to be dangerous.
Mr. Tobiason, an agricultural-chemicals entrepreneur from Nebraska with a bitter hatred for the government, said he sold about 2,000 copies of his self-published book a year as he moved from gun show to gun show across America. The book, which includes directions for making "mail delivered" anthrax, suggests that the knowledge necessary to start an anthrax attack like the one that has terrorized the East Coast is readily accessible.
While Mr. Tobiason's instructions fall short of what would be needed to produce the highly refined form of germ spores found last month in letters to Congressional leaders, experts find much to worry about.
"The guy who wrote this is very smart, very dangerous," said Ken Alibek, a former top official in the Soviet germ-weapons program who is now president of Advanced Biosystems, a consulting company in Manassas, Va. "We shouldn't ignore this.
"It's not sophisticated," he said of Mr. Tobiason's anthrax formula, "but this process is going to work."
F.B.I. officials theorize that the culprit behind the recent attacks might have been a home-grown loner with sufficient scientific knowledge and a deep grudge. Mr. Tobiason denies any knowledge of the anthrax-laced letters, and federal officials say he is not a suspect. But he is part of an American subculture of people with a profound mistrust of government, some of whom traffic in the intricacies of germ warfare.
Federal officials said they monitored Mr. Tobiason for years before the attacks began last month; indeed, there are indications that they recently stepped up surveillance of him and others who have shown inclinations toward antigovernment violence.
The talk from Mr. Tobiason and some who stopped by his table at the gun show reflected the conspiratorial view of government that some investigators believe may have been an ingredient in the anthrax attacks.
"I don't trust him completely, and I don't trust the government completely," a former nurse named Linda said of Mr. Tobiason after buying a $10 CD from him last weekend. One element of her mistrust of the government was the F.B.I., which she said is "taking away civil liberties all the time."
Mr. Tobiason, who is 45 and lives in an aging Dodge Caravan in which he travels the country, traces his own anger at the federal government to patent laws he said cheated him out of money and to what he said was surveillance by the F.B.I.
"If this government continues to do this to people," he said, referring to what he called years of F.B.I. harassment, "they're going to have a lot more Tim McVeighs and Tim Tobiasons."
The sale of survival and doomsday books is not unusual at gun shows and elsewhere, and the Internet is filled with advice on how to make explosives. What makes Mr. Tobiason's writings more dangerous, germ-warfare experts who have read it say, is that it offers anyone with $10 the ability to build crude biological weapons capable of killing thousands of people.
Those experts say Mr. Tobiason's 250-page book does not give specific directions for producing the finely milled anthrax that was sent to Tom Daschle, the Senate majority leader, and, in fact, contains some errors. The book deals mostly with the production of wet anthrax, though it does suggest a way to grind clusters of anthrax into microscopic pieces, which can settle into the lungs.
But Dr. Alibek said Mr. Tobiason's work "could be a step on the road," for someone intent on producing highly lethal anthrax.
Richard Spertzel, a former head of biological inspections in Iraq for the United Nations, said Mr. Tobiason's instructions would produce "a low- grade product" at best but added that the book, "ought to be damn near illegal, if it's not now."
Mr. Tobiason's work, which he said was drawn from military and biology books he borrowed from the University of Nebraska library, is written in mostly dispassionate, technical terms.
But his anger is hardly hidden. The cover of his germ-warfare manual includes the introduction: "Why pay to recruit troops and build factories to wage war and kill for you when nature can do it for free? Or, if you can make Jell-O, you can wipe out cities. Enjoy!"
In an interview on Saturday, Mr. Tobiason said he had made small amounts of pathogens including anthrax, though he said he had never used them to harm anyone.
He has written about a dozen books on military history and germ warfare and said he planned another soon that would describe how to make "huge scale" germ weapons.
"It will have some planet killers in it," he said at a Sizzler Restaurant after the show. "It will allow anyone to arm themselves with biological weapons in their basements."
Mr. Tobiason said he writes "to fight against dishonest government," and said that if he wanted to, he could initiate a far more deadly biological attack than the recent one.
"It would be a hard thing to do, but I'm prepared to do it," he said.
He said he would kill innocent people if he had to to defend himself. "All my morals and ethics are gone, just like the government's."
Mr. Tobiason has distributed his work widely. In June, he said, he left copies of his book at the offices of dozens of United States senators, including Mr. Daschle, a Democrat from South Dakota, Fred Thompson, Republican of Tennessee, and Chuck Hagel, Republican of Nebraska.
Mr. Tobiason said he was trying to get the attention of lawmakers for his complaints about the government. If Congress granted him a public hearing, he said, he would drop his plans to publish his next book. But other than a visit by federal agents, Mr. Tobiason said, his book did not get him any notice.
Mr. Tobiason, who grew up in Columbus, Neb., left Columbus High School during his junior year and enlisted in the Navy.