The Cartoon Guide to Biology is a fascinating, funny textbook. Larry Gonick's classic humor exists in spades, though it's sometimes covered up by David Wessner's biology knowledge. That's not a terrible thing: there's absolute loads to learn here. And it's pretty well arranged, building up from atoms to ecosystems.
But it's crazy dense, some sections almost impossible to parse. There's just so much terminology to take in, so much of it similar. Interons, enterons, exogens, ontogens, microgens - some of those are probably made up, but you get the idea. It's scientifically accurate, but hard to process unless you're actually a biology student. I mostly dug it as a huge nerd - the more casual reader might be intimidated.