I'm sure Gargantua and Pantagruel is tough in French, but I'd like to recommend it in English translation to people who don't speak French where it's just a lot of good fun. Plenty of older French works (or a lot less old, like Zola) that have been translated to modern English are just good, easy reads.

I'd assume that in French they're tough going for a while until you get your head 500 years back. I'm currently battling my way through Don Quixote in Spanish and though it's a fun and funny (not at all short) read, some of the long twisted sentences (and the old words) can be brutal. I'd bet, as above, that the English translations are breezy. I'm thinking about trying one after I finish this.

In French I'm currently working my way through Voltaire's Micromégas (which is short) but it's a hundred and some years after Rabelais and the prose is really concrete. Very short words and simple sentences. It's the story that's interesting.