Flash Boys: A Wall Street Revolt

High frequency stock traders will pay enormous amounts to shave small fractions of a seconds off of electronic communication time. Some of this could be beneficial for computer technology if they were willing to contribute back to open source projects. Alas, they like to keep their work very secret. After all, speed helps them to make make money. By being crazy fast they can perform time-base arbitrage, acting on changes in prices in one location before they have changed in another. They even brag about the benefits of ultra-fast speed, even when it does not benefit them. High frequency traders can use the speed to "get in between" a buyer and seller, making near riskless profits.
Flashboys covers a few somewhat related stories. In one, Sergey Aleynikov was arrested by the FBI and tried for "stealing" valuable source code from Goldman Sachs. This was portrayed as an incompetent witch hunt. He had uploaded code to a public SVN repo, with little attempt to hide his activity. (He could have easily walked away with all the code on a USB thumb drive.) The code he had was a mixture of open source code with the code written at the company. There was very little of the "secret sauce" from the company. He had been somewhat disgruntled that he had been unable to contribute back to the open source community. There were multiple attempts to make him an "Example". However, it seemed that there was no real damage done. (Lewis likens his activity to keeping a notebook of meetings at a job.)
The other story is about high frequency trading. There is the story of a cable from Chicago to New York built at great cost to be straighter to save a few fractions of a second off the time it takes a signal to travel. There are a few other stories about people that worked to help colocate near exchanges to be super fast.
The bulk of the story focuses on Brad Katsuyama, his experience at RBC and the people he brought together to create IEX. He gradually "uncovered" some of the oddities of high frequency trading. He got together a bunch of idealists to help create an exchange that would be immune to some HFT trading abuses. He identified some issues, such as high frequency traders taking advantage of the time it takes an order to reach different exchanges. IEX tried to prevent this by adding delays. They identified many of other bits of challenges. One thing they identified was the constant regulation/loophole loop. It seems that abuses in the financial system are enabled by previous regulation. The previous regulation was created to eliminate a previous abuse. And the path keeps going back.
The book does not go into great detail explaining high frequency trading. It does mention the great sums of money they are willing to pay for programmers and for speeds. Some have bragged about not ever losing money in a day's trading. The assumption is that they can make a few fractions of a cent in a few fractions of a second and just multiple that into real money without other noticing they have lost.