At first glance The Lucifer and Biscuit Hammer may not look like anything special, however looks can be very deceiving. It very quickly blossoms into one of the most engaging, funny, and at some times tragic stories that I've ever had the pleasure of reading.
The story may not be anything particularly original, but it easily makes up for its lack of originality with numerous twists and quirks that make for an enjoyable read that never fails to surprise, right up until the last chapter. Little things, such as the Princess' motivations for wanting to save the world, or unexpected character designs keep it interesting. One of the things I appreciated most about the story was its uniformity. There were no noticeable plot holes or contradictions that most manga are filled with. Most mangaka seem to make things up as they go along, which leads to inconsistencies in the story. It was clearly planned out, at least loosely, from beginning to end.
The humor is an integral part of the manga. The author makes use of an extremely dry sense of humor, that I'd expect from something out of Britain, not Japan. The thing is though, it works. I honestly laughed out loud a number of times, which is rare for me. It constantly pokes fun at typical shounen cliches, such as characters naming their techniques.
The characters are particularly interesting. The author makes very little use of character archetypes such as tsunderes, which have become increasingly common. Nearly every character is unique and given the attention they deserve. They're all given a proper back story, and each has very different reasons for why they fight. I also can't say enough about the growth that Yuuhi exhibits throughout the story. It was fascinating to watch him grow, and not just in the traditional sense. He gets physically stronger, yes, but he also matures tremendously throughout the story, all in an extremely natural way.
The art, while nothing impressive, is still quite good for the most part. The characters are all instantly recognizable. The fights are easy to follow. The author also makes extensive use of capes for dramatic effect. If something epic is happening, it's almost always accompanied by a cape or something similar blowing in the wind. I consider it to be the authors trademark, as it's present in all of his works that I've read.
This is one of my personal favorite manga, and I haven't talked to anyone who hasn't liked it. If you're still skeptical though, take five or ten minutes and read the first couple of chapters. I guarantee you'll be hooked.