"By the time the prospectus and agents were in the field [TATS was published in the US by the American Publishing Co., on a subscription (!) basis], a pirated edition of the novel had been on the market for four months. [I]t is [...] likely that [a Canadian publisher, the Belford Brothers] set [the pirated edition] from a hastily imported copy of the British one [published in Britain to secure a copyright there]. Their version of the novel was available in three prices: $.75, $1.00 or $2.25 -- considerably less than the authorized one would cost. And there was no way to keep pirated copies of the book from coming into America along steamboat and train lines. ... The copy in the Barrett Collection graphically indicates what [Clemens] was up against on its titlepage, where someone (the name has been effaced) recorded where and when the book was bought: on the steamer St. Lawrence, perhaps on its way into America, and in September, 1876 -- fully three months before [the American Publishing Co.] was ready to sell any copies on which [Clemens] could make money.
"The delay cost [Clemens] over $10,000, according to his own reckoning, and contributed to the book's weak first-year sales. ... [T]he fate of Tom Sawyer not only soured him on the American Publishing Co; it also seems to have discouraged him as a writer. During the next five years he published only one book." (https://twain.lib.virginia.edu/tomsawye/tomcomp.html)
Ultimately it comes down to whether one believes that the smart and creative don't deserve to extract profit from their creations nearly as much as the wealthy deserve to extract rent out of physical stuff they didn't create...
Perhaps their notion of property is more spartan than yours. :)
More seriously, property is a technology for resolving problems stemming from scarcity. If there is no applicable scarcity, then property rights are not necessary. Even more, if property rights in some arena effectively cause scarcity, as is the case for some forms of IP, then they ought to be abolished.
On this model, a particular copy of "The Adventures of Tom Sawyer" is scarce, where the right to copy "The Adventures of Tom Sawyer" isn't, since two people exercising that right at the same time need have no effect on each other. If they both want to sell copies, then the wider availability may lower the price of a copy, but this is only the same effect as two widely separated gold miners have on each other, and giving one miner the right to restrict mining of gold by the other would seem a weird application of property rights to many libertarians.