talk like a book

verb2

1. •
   (informal) To talk pedantically, or using excessively difficult or literary words.

   • "You talk like a book, my friend," said my lord, smiling, and puffing away at his pipe, "but you talked of saving time, and I do not yet know the purpose of your errand." — 1906
2. •
   (informal) To talk precisely and with authority.

   • But then no disgrace is attached in France to saying a thing neatly; whereas in England, to talk like a book is to give in one’s resignation to society. — 1878