I was twenty-seven years old when I first decided to read the classics. Most classics read differently than new literature. Many have archaic language, references I didn't understand, words I had never read (much less heard or used). You know how, for the first fifteen minutes of watching a movie or play whose characters have strong accents, it is hard to understand what the heck is going on? After listening for a while, you know what they are saying and by the end, you've forgotten that there was a language barrier at all. The same goes for reading popular literature, then, for the first time, delving into Dickens or Austen or Hugo or Eliot. The "thee's" and the inside-out construction of sentences can be hard to swallow.
Les Miserables was the most difficult book I have ever read--and I read it in those first few months after beginning my quest to be well versed in the classics. It was daunting, it was long, it was fantastic. It is not my favorite book, though I certainly place it firmly in my Top Ten. Mostly, I was proud of myself for closing the book without having skipped any of Hugo's sometimes tiresome tangents.
I just finished a book that was just as difficult, though not quite as wonderful, as Les Mis. It is The Odyssey by Homer. After The Iliad, The Odyssey is considered the second book of western literature. It was written it in something like 1200 BC. That's a long time ago. I have to say, while the story was not incredibly captivating (though it did keep my attention), I cannot overstate the historical importance of this book. I couldn't believe how many times I thought, "Oh, my gosh! So-and-so lifted that movie/story/plot straight from Homer!" There is, for instance, a reason that Penelope from Lost (Desmond's beloved) was named after Odysseus' wife.
Do you remember that super weird movie Spirited Away?
The parent's turning to swine? Totally Homer.
Wikipedia has a whole list of other things influenced by this story. Having just read the Percy Jackson and the Olympians series, all the Greek God stuff was interesting.
There you go. If you've always wanted to read it, I actually listened to an unabridged version; a translation by Robert Fagles read by Sir Ian McKellen. Tell them the MotherShip sent you.