Did you even read the book? The entire point is that some HFTs are given priority fills on orders that no one else has access to, even when the HFT quotes are worse, in return for kickbacks to the exchanges.
Also, I will reiterate: HFTs NEVER get fills on quotes that are worse than any other participant on the same exchange. That violates RegNMS, and is straight up illegal.
An allegation made in Dark Pools was that the existence of the order types was initially deliberately concealed from most actors in the market. The claim was well substantiated, from what I could tell.
[0] http://online.wsj.com/news/articles/SB1000087239639044398920...
"concealed", in this context, just means "too lazy to carefully read the documentation".