There's a famous, if a little unfair, Stuart Sutherland quote "Consciousness is a fascinating but elusive phenomenon; it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written about it." This book refutes at least the final sentence.
Truly fascinating on multiple subjects, the book approaches big questions from a novel angle. The writing on general evolution, cephalopods, and consciousness is exemplary, explaining difficult subjects clearly without dumbing down concepts or getting tied up in arcane jargon.
Well paced and with quite the twist towards the end (terms you usually here for novels) could not recommended strongly enough for anyone interested in intelligence, evolution, the mind, and the wonders of our fragile planet.