Well, sure the script still works. But all it does is install the official prebuilt binaries. And there have never been prebuilt binaries for the raspberry pi.
I suggest you use
https://archlinuxarm.org instead, as they provide an up-to-date ARM build of calibre that should work okay.
Well, at least Arch Linux makes it trivially easy to build your own if you would prefer something a little more recent than 3.0.0 (we're four minor versions ahead now), but even so that is much more recent than e.g. raspbian.