The first 10 issues are filled with parody of the sword and sandal genre as well as a number of other social institutions and practices. According to my sources, the series reaches for something greater than mere parody over the course of its 300 issue run, which means that I don't even know how good Cerebus can be.
If you are looking for a series which is well-written, expertly drawn, and endlessly creative, Cerebus is for you. I absolutely loved the first 10 issues and will definitely be reading the next 290 sometime in the future. Here's where Cerebus falls in the current First 10 standings: