Science-fiction novel: Journey across desolated planet with crystal mountain. Spoilers.

[Lopiben]

Warning: I read it in French and I'm not sure if it was original or translated...

I read this book while in high-school (it was a mandatory read) so I believe it's a teen/young adult science-fiction novel published before 2009.

The story follows a man's journey across what I remember to be a desolated planet (which is revealed to be the Earth at the end but I'm not too sure). He encounters different characters and situations, among which :
- A village that gets scorched by the sun every day because sun rays are refracted/amplified by a growing crystal mountain. I think the is mention of a lazy cat not moving on time and leaving nothing but a burnt silhouette at its place ;
- The crystal mountain is very sharp and people get cut/killed by falling/tripping while climbing it ;
- A community of people living on nets atop the mountain.

Would be very relieved to find an answer to this one, it's been tourmenting me for a long time now...