Okay, okay! I'll do it right.
Mushishi is a story set in a world very much like our own, specifically in Japan in a indistinct keyhole in time sometime in the not too distant past. Added to this world is the fantastic element of the mushi, a third form of being distinct from inanimate and living. The kanji used for "mushi" is formed of the kanji for bug the same way forest is formed of tree, but is just an archaic form of bug. This apparently isn't the first repurposing of "bug", so it must make sense in Japanese. Anyway, you've got to call them something.
In this world, we follow the wandering of Ginko, the mushishi. Literally, it translates as "bug master", where master is meaning one of great learning (mastery), not some sort of controller. Where he exerts any control over the mushi it is clearly by virtue of knowledge. Our hero cuts an odd figure in this past land with his Western style clothing and hair already white. These elements are meant to make sure he doesn't fit into his world, which is odd since he always seems to me to be someone who can find his place anywhere.
Not everyone perceives the mushi, but they are pervasive throughout the world and their existence leads to visible consequences. When these consequences become harmful, Ginko goes to work trying to fix the problem. However, the great variety of mushi means there is much to know about the mushi and some "cures" must be discovered while others are already known. This leads to a rich tapestry on which to paint the stories.
The stories themselves are often described as reminiscent of a Miyazaki movie, which can't be hurt by working with Miyazaki. I personally find it has the feel of a mythology. Each story may contain elements of great tragedy or happiness or anything in between. Each resolution is muddled by the complexities of the world. They do not live happily-ever-after, but they generally live successfully-ever-after which is a far more satisfying tale for me.
Volume 1: The stories in this volume are from a time when Urushibara was not yet working regularly on the series. Sometimes this shows in inconsistencies in the setting. This does not take anything away from the stories for me because each one can easily be taken on its own. As well, sometimes the art suffers from her inexperience but one is usually enjoying the story too much to notice.