Birthers, truthers, and other believers in conspiracy theories

Millions of Americans believe these bizarre stories — deeply and urgently. And in the Internet age, such fringe theories have, in many ways, gone mainstream.

It’s easy to ridicule conspiracy theorists like “birthers’’ (particularly those few who still refuse to accept that Obama was born in Hawaii, despite the recent release of the long form of his birth certificate) and “truthers’’ (those with exotic theories about who was really behind 9/11).

It’s harder to answer a thorny question: Why do they believe these things? That’s what Canadian journalist and editor Jonathan Kay attempts to do in “Among the Truthers: A Journey Through America’s Growing Conspiracist Underground,’’ an entertaining and informative — but ultimately uneven — tour of contemporary US conspiracy-theory subcultures.

Kay writes from a place of concern: “Truther theories may be nonsense,’’ he notes, “but the disturbing habits of mind underlying them — a nihilistic distrust in government, total alienation from conventional politics, a need to reduce the world’s complexity to good-versus-evil fables, the melding of secular politics with apocalyptic End-Is-Nigh religiosity, and a rejection of the basic tools of logic and rational discourse — have become threats all across our intellectual landscape.’’

Kay traverses this landscape, enduring interview after knotty interview with conspiracy-addled activists who prattle on for hours about How It All Connects. He introduces us to some memorable truthers, including Michael Keefer, an otherwise acclaimed Canadian academic and authority on Shakespeare, Descartes, and Christopher Marlowe, and Lubo Zizakovic, a 6-foot-8-inch former NFL defensive end of Serbian ancestry who became fixated on the US government’s deviousness after it struck against Slobodan Milosevic in the 1990s.

Keefer, Zizakovic, and their conspiracist fellow-travelers weave extended, so-convoluted-as-to-be-vertigo-inducing theories that blame 9/11 and other atrocities on everything from the Bilderberg Group (a real-life, rather boring-seeming annual meet-up of high-powered executives) to extraterrestrial lizard-men.

In addition to relating these stories, Kay provides useful history about conspiracy theories, as well as smart insights on the role the Internet has played in simultaneously connecting conspiracy-addled activists to each other and further cutting them off from the real world.

“Among the Truthers’’ has weaknesses that hold it back. It could have used more insights from psychological research, given that the discipline has made strides in understanding why people believe what they do and how they choose their sources of information. Many of Kay’s arguments — such as the claim that once people begin experiencing the indignities of middle age they are more likely to embrace conspiracy theories — would have been made stronger by citing actual research.

The book’s most annoying flaw is Kay’s tendency toward ideological axe-grinding, such as his disproportionate attack on left-wing postmodern academics. While it’s true that there are connections between truthers and some postmodern thinkers — both have tendencies toward agonizing circularity and take pride in embracing positions that no amount of evidence can refute — it’s a somewhat tenuous link. Modern conspiracy theories, as Kay writes, can often be explained as iterations of decades- or centuries-old schemas. If this sort of thinking existed long before Jacques Derrida, it doesn’t make sense to blame it on his disciples. But Kay’s focus on them saps a bit of the book’s intellectual energy.

Still, though, “Among the Truthers’’ is a valuable read for anyone unfamiliar with the contours of modern day conspiracist movements. Just don’t let the Bilderberg Group — let alone the alien lizard-men who really run things — find out that you’re reading it.

Jesse Singal, a frequent contributor to the Globe, can be reached at jsingal_globe@gmail .com, or followed on Twitter: @jessesingal.