We Are 100 by Nathan Timmel
You know the book is good when you start to root for the bad guy. :)
Evan lost his wife. The prices for the medication that could save her, got jacked up by the pharmaceutical company, so much that they could no longer afford it and she pass on... He is depressed and filled with the need for revenge. He blows up the board room, killing people responsible for the price rise and himself while making sure most innocent people are out of the building.
FBI agent Susan and newbie Michael are sent to investigate. What they soon discover is that Even is the first of many. A new website pops up, We Are 100, where after each crime is committed the is a video with explanation and confection.
It's up to Susan and Michael to find whoever is behind it and stop more people from dying.
The more they dive into the crime and people doing it, the more they discover, that they all had good reason for doing so. These are not senseless crimes, the people targeted are criminals who got away with it, who are still hurting people in some way. And the ones doing it, are people who are at end of their rope, who lost everything and are seeking revenge, or retribution.
It's the kind of story that makes you think and messes with you a bit. It delved deep into the gray zone between right and wrong, is it OK for criminals to walk free, to not get punished, is it OK that ordinary people always get the short string, that system seems to work for some people only. It made me root for the bad guy. :)
The other thing that makes the story great, is the partnership between Susan and Michael. Susan is an experienced field agent, who had many chances to be promoted but prefers field work to office and for Michael, this is the first assignment. Their almost instant friendship and mutual respect are what make their partnership work.
Once I started it, I couldn't put it down, I just had to know what happens next. :) The writing is top-notch. I was drawn into the story from the first page.
Highly recommend it!