That might help preserving the backup, but that contributes to the bigger problem (since you are supporting those who proliferate DRM). Voting with your wallet and avoiding distributors who insult users with this unethical garbage is a better approach.
It's even better that way, since you'll support sane authors and publishers who don't use DRM. I see no problem avoiding others. It's like global pollution. One can choose to avoid those who heavily contribute to it and prefer those who don't.
DRM isn't effective. Sooner or later the businesses involved are going to discover this. DRM doesn't actually inconvenience me (I'd be taking a backup anyway) so I don't mind publishers wasting their time pushing it.
If DRM was effective and got in my way then I'd pirate their books; not really from an ethical stance, but purely because of convenience.
Eventually the penny is going to drop and they'll realise that DRM causes piracy instead of preventing it and they'll stop using it.
