Books like A Gravity's Rainbow Companion: Sources and Contexts for Pynchon's Novel

This Companion was extremely beneficial in reading Pynchon's novel, especially giving reference to the social context and pop culture allusions that appear on nearly every page. However, I had to often set it aside, only referring back to it every so often since there was so much information that it impeded my forward progress in the actual book. I would recommend it to all readers, but it will come in handy the most on a second read. It should be noted that a first time reader may want to skip any commentary of the chapters as quite a bit of plot that won't occur until much later appears before each chapter. Well worth the money, a lot that I learned from reading this would have been equally interesting without Pynchon's novel as a reason to seek it out.