All those books lost... ultimately it is William and Adso who end up being the catalysts for the destruction. Had they not interfered that library and its books would have remained intact, to be freed at some later date.
On the other hand, it provided the diversion needed to save the girl and lead to Gui's downfall.
Worth it?
i find the burning library scenes especially horrific.
worth it? no, certainly not. the lives of Gui and the girl cannot justify the loss of knowledge and wisdom the books and manuscripts would have provided to future historians and researchers. while i found the library's destruction predictable in the plot i did not expect Adso and William to be directly involved.
"only one food for the rest of my life? That's easy, cherry-flavored Pez. No question about it."