I'm always reading something, usually multiple books at a time.
I really had no idea about HFT (high-frequency trading), let alone "dark pools," but nonetheless, appreciated Michael Lewis's telling of a disaffected group of finance guys looking to devise a new stock market immune from the loopholes that allow insiders to game the system, to the detriment of the average person with a retirement fund. No need to be a finance wonk to appreciate this book. Lewis does a great job explaining a murky topic.