At the New York Times Sunday Book Review, humorist and journalist Henry Alford gives advice for borrowing books, giving books as gifts, and commenting on books when you recognize the one the stranger across from you on the train is reading (conclusion: you should probably keep your opinions to yourself). One of his best tips:
Unsolicited books should be given free of any air of obligation or expectation. The best sales pitch I ever got for a loaner was the friend who handed me “Fight Club” and said: “You might love this or you might hate it. My ego is not involved. Explore without constraints.”