By Hidekaz Himaruya. Released in Japan by Gentosha, originally serialized as an online webcomic. Released in North America by Tokyopop.
The concept of anthropomorphized countries is nothing new, as anyone who's seen Uncle Sam can tell you. Indeed, the year Hetalia came out, another Japanese webcomic artist was drawing various countries and their own (slightly more serious) troubles as "Afghanis-tan". But Hetalia's the one that really took off, and this title has been highly anticipated ever since Tokyopop announced it. It has a huge fandom in both Japan and the West, one which delights in fanfics, fanart and cosplay. It was, in fact, the most obvious license ever.
But is it any good? Well, mostly. It was originally a webcomic, drawn without much thought to a legacy, and that shows in the extremely scattered nature of Volume 1. (It also shows in the art reproduction, some of which is simply miserable. I'll have to assume that this is the case with the original Japanese as well.) There is no 'plot' as such to this, just Italy and his other country friends goofing around or getting mad at each other. Its 4-koma nature means the humor can be very scattershot, with pages going by with only weak gags. And it is, let's face it, one long ethnic joke.
That said, there's a giant goofy charm to this manga that can't help but carry you along. The premise almost seems to dictate this, as anything other than 'goofy comedy' would end up being even more hideously offensive. Theoretically, this is about the three Axis powers joining and starting World War II, but that's barely touched on except in the vaguest way. There's certainly nothing remotely mentioning the Holocaust. This is European History as dumb knock-knock joke, and it works better for that. Germany is meant to be the country as a whole, not Nazi Germany.
Talking about characterization almost seems to be pointless, but it's there. Italy is truly stupid and annoying, in the best comedic hero way. Most of the jokes either riff on obscure historical trivia or talk about their country's stereotyped loves and hates. Italy loves pasta, Germany is obsessed with order, America loves Cheeseburgers and being "the hero", etc. There are teases of relationships I'd like to see developed more - Austria, Hungary and Prussia in particular were quite funny and I hope to see more of them. I was also rather surprised at the occasional serious series of strips, especially Hetalia's version of the American Revolution, which comes out as a younger brother realizing that he's grown up and doesn't need his older brother's help anymore. It was actually rather touching.
It should be noted that the fandom for this series is largely yaoi-oriented. There's no actual evidence of this in the series per se - indeed, there was actually less shippy tease in this volume than I'd anticipated from hearing about it - but you can definitely see why it attracts said fans, and I certainly get why they'd be all over these guys. Hungary was the only female in the entire volume, but I do hear that future volumes introduce the occasional female country as well.
Overall, I'd say this was definitely worth a look, though if you take offense at the basic premise of WWII Countries acting like idiots than it's probably not for you. For all its historical footnotes it has no particular desire to be historically accurate, but I don't think anyone is looking to Hetalia to teach them anything. There are lots of pretty boys being silly here. That's all that matters.