IGN has a nice five-page piece about the interplay between science fiction and fantasy literature and video games. Halo gets a couple of mentions, not surprisingly, most of which fall on page five:

Bungie's Halo series has become one of the most broadly known sci-fi games across the globe, but it's a significantly different take on the first-person genre than the Half-Life series. It draws from different sources as well. Halo's influences have been exhaustedly discussed, and Bungie has done little, until recently, to quell the debates. Halo's literary influences abound, ranging from Larry Niven's "Ringworld" and Ian M. Banks' "The Culture," both of which may have influenced the ring-like worlds called Halos. The drones in Halo are similar to the Buggers in Orson Scott Card's "Ender's Game," as is Halo's SPARTAN program, reflective of the super soldiers from the same book. Even Halo's viral Flood species rings familiar to similarly destructive creatures from "Ender's Game." It's also been suggested that Master Chief, aka "John 117," was formed from ideas found in Christopher Rowley's Starhammer, which featured a genetically altered man by the name of Jon 6725416.

The entire article, though, is well worth a read.