I bring a book, along with my notebook and pen, everywhere that I go. Of course it’s very rude to read at the table instead of speaking to your friends and family, but in any situation where it wouldn’t be faux-pas to use a mobile device, I think that it’s fine.

That said, manners are a context dependent social construct and truly it is the case that “impolite” is whatever your peers deem impolite or anti-social. So although it is logically incoherent, it might be the case in your family that reading is rude while scrolling social media isn’t.