"This is a song about helping your partner to get through life and vice versa. Great relationships need management. In a great relationship that management is shared.”
- Bono about Book of your Heart, 2017
did you know
The lyric "3:33 when the numbers fell off the clock face" from Unknown Caller is a reference to the Bible verse Jeremiah 33:3. Bono refers to it as "God's phone number".