Avoiding hyperbole while writing about a possible medical catastrophe is no easy task, but David Kirby has created a fine balance of investigative and personal detail in Evidence of Harm. Combining stories from the parents of autistic children with reports, speeches and studies from researchers, pediatricians and government officials, he creates a picture that is as terrifying as anything dreamed up by Hitchcock. The topic at hand is determining whether high levels of organic mercury present in an inexpensive preservative used in vaccinations can cause either autism or autism-like symptoms. Kirby's in a delicate position, searching for the truth between frantic parents (he focuses on the founders of political action group Safe Mind) and the self-protective pharmaceutical industry (the author thanks the nameless person who placed a pro-Eli Lilly litigation rider into the Homeland Security Act of 2002). He's also honest enough of a reporter to admit to the temptation of deciding mercury is the culprit behind a range of disorders, even in light of some inconclusive test results. The ultimate truth isn't clear, and Kirby is direct about each of the reasons his sources have for their biased opinions. While some of the straight research reports will likely to go over the head of anyone not well versed in the terminology, the book is never dull--there is a continual urgency in the material that resists pedantry. However undecided the experts, readers will likely land firmly in one angry camp or the other. Jill Lightner