booktv is taking a tour of that exhibit, and joining us is roberta schafer who is associate librarian for the library of congress. ms. schafer, why do you call it books that shaped america? >> well, we actually call it books that have shaped america as opposed to some the other words we considered like changed america because we think that books slowly have an impact on american society, and shaped seemed to be the better word to imply that kind of con connotation. >> when you think of the word shaped and what you just said, what book in this exhibit comes to mind -- >> well, actually, that's the fabulous part of this exhibit. no one book is shaping america. so many books have had such a profound influence on american culture and society and, indeed, the very essence of what america is. it would be impossible, and it really would be improper to pick one book from the 88 that are here. >> okay. there's 88 books. it starlets out, the exhibit starts out with "common sense." >> yes, it does, although the earliest book is actually ben franklin's book on electricity. that's 1751. so we have