Good if you want half the picture
I've read the book. It brings up important points. The film does the same for lazier people.
But overall the implication it makes that this disinformation is coming from one side, industry or conservative politics, has been debunked.
One only has to look at GMO and US gun issues, and references to the so called "nudge" by Jonathan Gruber or others to understand this "Bu11sh t" and promulgations and recourse to junk science is becoming common enough for both the left and the right, industry and politicians, on both sides of any debate.
Moreover there is also increasing data rejection and inversion of objective core facts clearly exhibited to the same degree by left and right, and even by the most educated, by voters on either left or right. That rejection of fact is absolutely determined by a person's politics.
For example the anti GMO movement is complete quackery and based on junk science. Over 70% of people on the left in the US are certain there is peer reviewed work showing a danger to human health from GMO consumption, when there is not one single peer reviewed work showing this. Even higher numbers in Europe have the false view.
On guns we have junk science "studies" that indicate states with more guns have more gun violence, yet those studies are comprised of 2/3 suicides, where the researchers are indeed counting gun suicides more prevalent in high gun owning states, but don't count suicide and self inflicted death by other means elsewhere when that is higher in same demographic groups with less guns. Indeed the results get inverted when you control for suicide properly and similar states with more guns have a lower overall murder+suicide rate. Studies on that issue are bought and paid for by billionaires on one side of the issue as well.
In the US the gun murder rate has fallen 58% between 1993 and 2014. In other words approaching a plummet to 1/3 of the rate it was just over 20 years ago. Yet persons on the left, and more so the higher educated they are, literally invert that core metric's dramatic plunge and think it is up. There are scores and scores of youtubes of pro gun control experts interviewed on news shows, clearly implying an increase, some stating an increase (!), when a profound decrease in gun murder has occurred.
Not only does Merchants of Doubt just look at this from the perspective of the left's causes ,it also absolutely ignores the social science on views formulation, which shows the prevalence incorrect views on both sides of the political culture, and of how these views are incorrectly formed.
I think anyone viewing this film should look at the following article. It does not slam the authors of "merchants of doubt" but shows their many serious inconsistencies, and how they are a bit anti science themselves when it comes to the social science on political bias within science and in audiences internalizing science and data.
http://www.academia.edu/4754580/Debunking_skeptical_propaganda_Book_review_of_Oreskes_Conway_Merchants_of_Doubt
Also consider instead of this shallow film, one might also look a the Yale Cultural Cognition Project's much more serious and lucid work:
http://www.culturalcognition.net/