I'm currently reading The Soul of an Octopus and it's really joy inspiring. Part pop-science, part memoir, part inter-species romance. If you just come in for science you'll be annoyed by Clever Hans effect and confirmation bias, but that's all pop science writing on animal intelligence.
if anyone’s interested in a science fiction take, Steven Baxter’s “Manifold: Time” has a subplot involving intelligence-enhanced cephalopods. It’s one of my favorite hard sci-fi reads…
http://amazon.com/The-Soul-Octopus-Exploration-Consciousness...