The Washington Monthly has compiled a list of suggestions. Some of it is 200-proof left-wing nuttery (Debra Dickerson recommends Howard Zinn), but it also includes Jim Pinkerton’s recommendation of Friedrich Hayek and Nathan Glazer on a book about India.
If I could assign a book, I might go with Who Really Cares by Arthur Brooks. Liberals are usually surprised, and often outraged, by what it reveals.