Read "Flash Boys" for a better insight into how much difference variable latency between exchanges and clients makes to the profitability of fast execution of trades.
Patterson's _Dark Pools_ which tells the story of Island and the ECNs and the advent of automated trading. Patterson is more ambivalent about HFT than Kovacs, and does a good job of explaining the Core Wars phenomenon of modern trading from '98 to the mid-'00s.
https://en.wikipedia.org/wiki/Flash_Boys