What use is an ipad or ipad mini to someone with an iphone and macbook?

I'm thinking of getting an ipad mini or ipad 2 for someone who already has an iphone 5 and macbook pro. I don't know how useful it will be since they are not likely to use it outside of their home and i'll be getting the non 3g version so it won't be much use when they take it out anyway.

I use mine for bookreading, and there's no way I'm doing that on a phone or computer.

Well the only difference would basically just be the bigger screen than your iphone5 maybe get a cheaper regular tablet so that you aren't spending a lot but you also get a bigger screen. There's actually a lot of good tablets out right now that are pretty cheap

Well an extra iOS device to spread across app installs wouldn't hurt. That personally the reason why I'm looking into getting one myself. I have the same 2 devices as well currently.

Could think of it as an in between device.