Here's why:
* Humans leave Earth: The story starts with humanity fleeing a dying Earth and settling on a new planet.
* Glass Plants: The new planet is inhabited by plants made entirely of glass, which are the only source of food.
* Syrup Food: The glass plants produce a sugary syrup that serves as the primary food source for the colonists.
While other books might feature similar elements, "The Glass People" aligns perfectly with your description. It's a fascinating and thought-provoking story about a society struggling to adapt to a strange new world.