What is Giles Corey's complaint about his wife?

Giles wife reads books..... something he cannot understand.

Giles: Mr. Hale, I have always wanted to ask a learned man - what signifies the readin’’ of strange books?
Hale: What books? Giles: I cannot tell; she hides them, Hale; Who does this?
Giles: Martha, my wife. I have waked at night many a time and found her in a corner, readin’’ of a book. Now what do you make of that?