Terribly crafted, but surprisingly useful.
Inheritance is, in a word, pooptastic. Okay, so in a made-up word. But there are a couple ways that the series can benefit us. The first way is obvious, and many have pointed it out, but I say it nonetheless: doorstoppers. Paolini's pointlessly longwinded writing has made for some books of impressive weight. Maybe they can be used to hold down buttons in order to solve in standard dungeon puzzles? They're probably cliche enough.
The second use is as a beacon of bad writing, nonexistent research, and just plain wrongness (as in Uncanny Valley creepiness). As I am working on my first foray into writing a full novel, Eragon has shown me what a bad writer really is capable of. I am at once shown errors that no writer should make, and encouraged in that even a bad writer can make a fuck-ton of money if they make their story nice and flashy. So, being a hack, I can look to Paolini as inspiration.
Oh, shit. I forgot that his parents ran a print company and actually produced that monstrosity. And after that, the pretentious snot was lucky enough to have a Knopf executive's nephew (I think it was a nephew) read the book and fall in love with it. Yeah, I think he was an elementary schooler.
The last use is to provide that magic moment Stephen King described, when you put down a book and say: "Boy, that sucked! I can do better than this, and this got published!"
Anyway, I can hardly begin to bash the cycle adequately. If you want someone's much better thought out criticism, I recommend Kippur's Eragon Sporkings. They're hilarious, and go very far in depth. Thank you for reading, unless you are Christopher Paolini, in which case: PLEASE STOP!