Complex sentence: It also contained much material that could be considered background for his other novels, including a detailed description of the protagonist's treatment to avoid being banned to Coventry (a lawless land in the Heinlein mythos where unrepentant law-breakers are exiled).
Split into simpler sentences: It also contained a large amount of material that could be considered background for his other novels. This included a detailed description of the protagonist's treatment to avoid being banned to Coventry (a lawless land in the Heinlein mythos where unrepentant law-breakers are exiled).