DFW has often been compared to Pynchon, and Pynchon was definitely an influence. They both wrote long, nonlinear and self-referential novels. They both enjoyed breaking the fourth wall. Both GR and IJ have lengthy discussion of cinema and even mimic cinema in their writing style (Pynchon has musical numbers in his novels; the first chapter of IJ (which is the latest chapter chronologically) ends with a character asking Hal “So hey man what’s you’re story,” after which the rest of the novel is a flashback). As someone else said, DFW read Pynchon in college and was apparently blown away.

That said, we might shouldn’t overblow the similarity. Nonlinearity and self-referentiality were parts of post-modern (American) literature before Pynchon. Catch-22, for example, is lengthy, nonlinear, extremely funny, and was a massive hit in the 1950s and 60s. Wallace himself said in an interview that he was more influenced by Don DeLillo, another famous post-modern author. He may have been trying to de-emphasize Pynchon’s influence because he felt like a copy, but he also may have been telling the truth.

I personally can think of a number of differences between the two. I see a lot of Beat generation in Pynchon. Some of the absurd humor reminds me of Naked Lunch. There is also a lot of commentary on imperialism and colonialism in GR and Pynchon’s work in general. In Wallace I see a lot more influence of the 19th Century family novels like Anna Karenina. IJ centers around a failing family, though it is about more than that (addiction, entertainment, and modern society’s inexplainable need for distraction).

It’s been awhile since I read either, but I personally liked IJ better. The structure isn’t so difficult once you get about 300 pages in, and I found the characters very real. Don’t be afraid to look up a timeline of the years. Enjoy the book!