My wife sent me these that she has read and recommends:

Textbooks:

Cephalopod Cognition by Anne-Sophie Darmaillacq (Editor), Ludovic Dickel (Editor), Jennifer Mather (Editor)

Cephalopod Behaviour 2nd Edition by Roger T. Hanlon (Author), John B. Messenger (Author)

Personal anecdotes:

The Soul of an Octopus: A Surprising Exploration into the Wonder of Consciousness Paperback by Sy Montgomery