For some reason, a number of newspapers have been reporting, as if it were something unusual and exciting, the sale at auction of a C18th copy of Aristotle's Masterpiece, with claims that this was a 'banned book'.
I am not sure what 'banned' means in this context: there was no context in the UK for 'banning' books but there were certainly titles that, at least in the wake of the 1858 Obscene Publications Act, reputable publishers and booksellers might have been cautious about vending without provisos that they were for a restricted audience such as doctors and lawyers. Even so, prosecution only occurred if somebody made a complaint to the authorities.
However, the Masterpiece was not produced by mainstream publishers but as part of a low culture of ephemeral productions, and sold in a variety of venues including 'rubber goods shops', which also sold contraceptives, abortifacient pills, etc. It may well have got swept up in police raids along with other literature considered dubious and falling within the parameters of Obscene Publications Act, but there are no famous trials involving its prosecution (though probably because the dealers selling it considered paying the occasional fine part of the cost of doing business, rather than seeing the issue as a matter of principle, as with the Bradlaugh/Besant Fruits of Philosophy case).
The fact that numerous copies of various dates come up when searching Bookfinder and are held by a range of libraries featuring in COPAC suggests that for a supposedly banned book a significant number of copies were in circulation in the UK (including in Welsh) from the late C17th until at least the 1930s, when it is listed alongside the works of Marie Stopes and Theodor van der Velde in the mail-order catalogues of rubber goods firms.