Comics occasionally cause me to crave a good stiff drink...
The point of the book, and the reason I referenced the comics I did (ie, comics without tons of continuity, with the exception of 52) is that the modern narratives that we follow, be they Sopranos, Survivor, Prison Break, Heroes, 24, etc. are more complicated and concern more relations between individuals and groups and demand more of an audience. This is what DC continuity does, in a way, if you see the entire monthly output of the company as one "series". But I don't read enough modern superhero comics to know if they are even half as complicated (?) as tv or some video games.
I haven't read the book except for some excerpts, but its claims aren't particularly far-fetched. I've certainly noticed how video games, for instance, have made me better at solving puzzles and operating a computer, for instance (in a roundabout way, they even taught me how to build one: in order to play the more graphically demanding ones, I ended up building my own, and continue to make them for friends and myself).
As far as comics go, I'm sure all reading material is beneficial to you - even the bad stuff gives you standards to judge by. Certainly complicated continuities help you use your memory, and beyond that, speaking for myself, comics taught me a lot of vocabulary as I was growing up, and also helped to place it in context. This was certainly helpful to me as I was growing up in a trilingual environment; comics helped me juggle the three languages I was struggling with, and also showcased the cultures that produced them.
Some words and expressions I can remember first encountering in comics: "Alter ego", "By dint of...", "Rankle", "Annihilate", "Ultimate Nullifier".