Brown takes one topic for each work of his and presents a thoroughly researched expose thereof with a thin veil of a murder mystery, and this time it is about the very factual problem of today, where all dire scenarios of future have all sorts of interconnected roots with one chief problem, overpopulation. Also, in this work he goes back to his first two works in the sense of a background from history, art, literature and so forth, deeply rich and contextual for the problem. Da Vinci Code had Leonardo Da Vinci and his works along with history of Europe, west Asia and Rome of two millennia, while Angels and Demons had church and Illuminati and a short lived pope that might have been murdered; this work has Dante, Virgil, Vasari, bible of course, and other works related to concept of hell and inferno as depicted in various systems related to church. Needless to say he portrays east vs west in a very limited way as church vs Islam.
Inferno here is both the problem - problems that come together in the current scenario and their future outlooks for earth and humanity - and solution thereof. Any solution to human population growth and its devastating effects on earth of today must deal with question of reproductive rights and of course resulting human rights of survival, and in past this was taken care of by nature with various calamities such as plague or war and deaths of infants and mothers in childbirth - all of which are today receding with increasing of human knowledge and widening of consciousness, to the extent that very concept of an inevitable death past a certain age is now challenged, and natural relief from overpopulation can only be a far lower rate of reproduction.
For obvious reasons such as racism that is still very rampant, this possibility of such a tool for culling of reproduction cannot be in hands of a powerful institution that might thereby use it to wipe out population seen as unimportant, and one can imagine scenarios where a government in possession of such a tool may wipe out a few poor nations. Or continents.
So here a genius scientist works alone to solve this, and leaves clues about his work admittedly due to an egotistic need to be acclaimed for relieving humanity from the hell it is inadvertently descending into - overpopulation, global warming, wiping out forests and species galore, and effects of any and all of these.
Most people in any glimmer of this assume it is a virus related to a plague that is being released and race to stop it, finding out that it is too late to do so, and trying to discover what virus, what effects, what if any solutions might exist. What they discover however that it is a virus quite different from what they all imagined, bringing not death but a permanent solution to the problem, and is in the long term benevolent. The remainder is sort of anticlimactic, and leaves only one question that most readers would not realise exists.
Populations culled at a certain rate worked for the best is an observation and the virus goes towards affecting it in a certain way, in Brown's Inferno. However, he fails to see that in reality his solution might cull population at twice that rate at most, and certainly there would not be any guarantee that it could be limited to the rate he states is ideal, unless a very organised reproduction was arranged throughout the world. Sheer calculation and a small error that he has perhaps missed.
