speak by the book—speak accurately, with care as to facts:
- I knew him for many years, and I speak by the book of the man. He could write nothing that he did not at least feel to be true.
speak like a book—use literary or pedantic language in conversation:
- “If you can contrive to affect to be angry with him for his extravagance, it will do good.” “You speak like a book, and I’ll try my best.”