Maybe it's because I ride a bus but not a train. I've never seen a 'raised eyebrow' when someone pulls out an iPad or other larger-than-phone device to read or otherwise pass the time with.
When I commuted into and around NYC, reading on a larger-than-phone device was always totally unremarkable, so I'm confused. There's probably a cultural difference here that's interesting.
My phone is not a great reading device. Far too small. I do have ebooks on my smartphone in case I ever needed something to read, but the compactness of the phone made me never do so.