Importance of books

In Act I, Giles Corey questions Reverend Hale, "Mr. Hale, I have always wanted to ask a learned man - what signifies the readin' of strange books?" (Act I, p. 40). Giles continues to explain his wife has a strange habit of reading, but does not reveal what books she reads. Later in the play, this fact will be used against Martha Corey as basis of accusations of witchcraft.