Liquidity providers get paid to trade on most exchanges (maker-taker model).
ETA: That's not to say this is a good book. It's not. I'd recommend Vidyamurthy's Pairs Trading and Harris's Trading and Exchanges, but there really aren't many good books on this style of trading--anyone who knows how to do it well has no incentive to write a book on it.
ETA: That's not to say this is a good book. It's not. I'd recommend Vidyamurthy's Pairs Trading and Harris's Trading and Exchanges, but there really aren't many good books on this style of trading--anyone who knows how to do it well has no incentive to write a book on it.