I'm of the opinion that Azuma's previous series Azumanga Daioh simply cannot be bettered. There is just nothing as unflinchingly, overwhelmingly and irrepressibly nice on the planet.
That said, this is a fine successor to Azumanga Daioh, and fans will see a lot of the characters of that series momentarily floating to the surface of Yotsuba&!; indeed, most of Yotsuba&!'s characters could be called remixes of Azumanga characters.
That's no bad thing. The key to Azumanga Daioh was the perfect characters, and Azuma's clearly wise to this. Basically, what you get with this is a surreal sitcom to rival the likes of Fawlty Towers, but in the manga style, and perhaps more importantly in the Azuma style; simple, even childish art style at times, but all the more effective for it, and an episodic narrative that appears to have no real order to it but which in fact is simply the way real life works, reflected in the story. In this way the characters remain the heart of the book, rather than any overarching plot as such. As well as more of Yotsuba's antics as we saw in the first book, this volume contains a little more exploration of the considerably less peculiar, but still not really describeable as normal, family next door.
It's a fantastic bit of unabashed fun. Laugh, smile, be fond, forget your troubles. This ought to be a prescribed medicine for The Blues.