Recently released is The Flame Alphabet by Ben Marcus, about a world in which the language of children -- the simple act of their speaking -- begins to kill their parents. The idea of language having a deadly physical affect on people is a great one, ripe with all sorts of possibility. Mr. Marcus tells his own compelling story about it, but here are three other books with a similar concept at their hearts.
Pontypool Changes Everything by Tony Burgess - a virus transmitted through conversation turns the infected into rampaging killers. There was also a movie based on this one.
Lullaby by Chuck Palahniuk - a children's lullaby, when recited, can channel a targeted psychic deathblow.
The Man Who Collected Machen by Mark Samuels - a book of weird tales featuring several stories of toxic language, including one called "THYXXOLQU," in which gibberish begins to take over all written words.