VM: I’d say the best fiction is not the best fiction because it is challenging- rather, it is the best fiction sometimes in spite of it being challenging. Of course, the challenge can sometimes contribute to the quality, but many times just the fact that it’s still gripping and fascinating despite being difficult to read is a credit to the author.
I love Les Miserables. While in and of itself it’s not a mentally challenging book to wrap your mind around, it is long-winded and occasionally confusing, especially when you’re a lot more used to Terry Pratchett :). Even so, it’s a fantastic book and I really enjoy reading it, even if I occasionally only end up skimming the fifteen chapters about the French monastic system and ergot mold. I definitely think that’s a credit to Victor Hugo (the well-told story, not the ergot mold).