Every book has a unique number used to identify them, the ISBN (International Standard Book Number). If you can figure out the ISBN of a book, it becomes an easy search term for piracy, because now you aren’t looking for a long title, you’re looking for a unique number!
Most bookstores will list the ISBN of a book on their website, so that step should be pretty easy.

Then to commit the piracy, you can often just google the ISBN + filetype:pdf and get a free PDF pretty frequently.
There is also library genesis (libgen), where you can look up pirated books via their ISBN, which has a super wide selection.
And if even libgen does not have it, you can try torrent trackers (read up more on !piracy )

Of course most of those options are legally questionable or illegal depending on where you live, and I of course would not recommend you actually perform them ;)