This human reluctance to spurn a tall tale that we would like to be true is worth understanding, and the project on which Will Storr embarks in The Heretics: Adventures with the Enemies of Science is therefore an admirable one. In seeking out creationists and homeopaths, Holocaust-deniers and past-life regression therapists, he seeks not to mock strange convictions, but to get inside the minds of those who hold them.

The result is an entertaining journey dotted with some fascinating reportage. Storr tells good stories, which sometimes shed interesting light on the psychology and delusion of belief. His account of a tourist trip around concentration camps, with David Irving as a grumpy and self-absorbed guide, is outstanding, exposing both the historian's staggering ability to deceive himself, and a surprising diversity of behaviour among his neo-Nazi acolytes.

Other strong chapters detail morgellons – an itching syndrome that sufferers claim is caused by mysterious fibres, but which medicine does not recognise – and a damaged woman who disowned her family after "recovering" memories of Satanic abuse. In each case, Storr remains sufficiently dubious of improbable claims, but sufficiently open to the genuine distress of those who make them, to explore alternative explanations for their plight that fall the right side of Occam's razor.

It is the very quality of these chapters, however, that makes Storr's book disappointing and infuriating. For having shown he can achieve the kind of sceptical distance that makes Jon Ronson and Louis Theroux such effective chroniclers of weirdness, he casts it aside in an indulgence of wishful thinking. It is not enough for Storr to consider why people believe weird things; he also wants to challenge whether these things really are weird. He seems to accept, deep down, that they are, but he doesn't want to admit this. He is like the child who still wants to believe in Father Christmas, but who is just old enough to know better. Life would be more magical, more fun, if the story were true.