Absolutely not. All book burning (unless we're talking like, phone books) is disrespectful and honestly rather frightening. The written word is more than just paper and print, it's the sum total of what our civilization, and humanity in general, has achieved. Maybe some day in the future no more books will be printed and everything will be kept purely in digital form, but that just makes all the books that WERE printed even more valuable!
I do assume libraries and the like need to destroy books now and again because they've simply become too broken to be used, sold or lended. And I also assume that sometimes, say, a book store can't possibly store a large print run of something shitty and they can't get rid of them for free even, and just have to give them to the recyclers. I am not saying that this kind of 'necessary' book destruction is somehow automatically bad (books aren't sacred in that sense), but just arbitrarily burning a book for no practical reason? That IS bad.
I've got books in my shelf that are nearly a hundred years old. I've held books that are older than that, considerably older. Dictionaries, random school books, a book of latin quotes. Today, they're treasures. A hundred years ago, they were just books. That book you're burning? A hundred years from now it'll be a cause of wonderment. No matter its apparent lack of merit or value today, wilfully burning a book is just...inexcusable. Geeze. People really don't react against it more strongly than this? Egads.
Anyway. No. I would never burn a book. I -could- consider putting it into the paper bin if it's truly unsalvageably broken, where it would at least be recycled for its pulp. But burning it? No.