https://en.wikipedia.org/wiki/Steal_this_book
Booksellers (who dared sell it) typically kept it behind the counter since the intended audience did steal it.
The antics of Abbie Hoffman were legendary: He once brought the New York Stock Exchange to a halt for several minutes when he threw hundreds of $1 bills from the visitors gallery onto the NYSE trading floor, and all the brokers scurried around grabbing the money. The gallery was separated from the trading floor by bullet-proof glass shortly after his visit.
The book is chock full of hacking techniques, by which I mean using systems (subways, payphones, shelter, society, politics) in unexpected ways. Contrary to popular belief, the content of the book is mostly legal things one can do to live for free.
Reflecting the times, Hoffman's politics are very socialist, not libertarian. However, the book would be well appreciated by HN readers. I'm sure there are free copies easily found on the web.