Just don't...
Any book with the name or any sort of content of "travel hacking" is a clickbait bllsht.
The so-called "hacks" would be like: "Don't ask taxi service from people at the airport, download Uber or Grab in Asia".
"Pack wisely, to avoid paying extra for checked baggage"
"smile at the gate agent and maybe they will upgrade you to first class, as well as clean your house, and buy your grandmother a new car"
Read reputable forums, know your sources, and then you will find some strategies about what kind of travel hacks you want.
For example there are some airlines with insanely hackable award flight tricks. However if you just start flying, and have 0 miles for XY airline, then those hacks have 0 value for you.