I found a Machzor in a prison chapel library, there are no Jews there. Should I take it?
I found a Machzor for Yom Kippur in the prison chapel library, amongst goyish books. Since some inmates take the books and desecrate them and since, as far as I know, there are no Jews there (I do not know for sure) can I keep and use the book even though it has a stamp inside saying that it is prison property?
You should speak to the librarian and ask him if you could keep it. If he doesn’t let, and you’re concerned that it might be desecrated, it’s a mitzvah to buy the sefer so that it shouldn’t come to disgrace.
If no such concern exist, then it is worthwhile to leave it there so it could be used in the future by Jewish inmates who might be sent there.
שו”ע או”ח סי’ ל”ט ס”ז ויו”ד סי’ רפ”א ס”ב ועיין מג”א רסי’ תרמ”ט שאפי’ אתרוג (דלית בי’ קדושה קודם שברכו עליו ראה מחצית השקל שם) צריכים לקנות מהם שלא יבוא לזלזול.