Burning books can indeed be beautiful. I've destroyed badly written police novels this way, and once you overcome the nagging notion that burning books is naughty, it's actually very fun.
I'd never purify by the flame any book that didn't really deserve it on purely literary grounds; it must be really badly written trash. I think anything by Dan Brown would burn up nicely.
I would say I have experienced a similar feeling in a recent effort to reduce my fingerprint, deleting files on my computer/google drive that I don't use (which can be easily found over the internet). It just feels good, destroying information.
You're silly. In all seriousness, however, I did lose all my books to a fire so I can truly appreciate yet another advantage of e-reading: the digital books themselves are implicitly indestructible.
An secondary advantage of pysical books is that they're much more beatiful to destroy. Burning books make a striking image, and not only because the ominous historical connotations.
Nobody would be bothered by an ereader melting in a fire or being crushed by a steamroller (unless it is their own, of course!) Even CDs were better for that.