Your sister made a good recommendation to you. However...(there is always a "however" you know.)

As far as I know, there is no legitimate digital version available. Most of the eastern manga publishers are even more frightened of digital than the western publishing houses. They try and maintain absolute control on all legal means of their media (which is fine as long as they don't simply swing their swords at the sea) which at this time does not include ereaders. Yet.

(Several companies are actually starting to introduce readers that handle the lettering and formats native there. If they catch on then I'm sure we will start to see more content released. Especially if the manga creators themselves see a market in it.)

The manga itself doesn't really flow very well (in my opinion) on a small screen. On a larger screen it works well but that was because all the details and dialogue was easy to grasp and read without spending valuable BPUs (brain processing units) on figuring out what was what. But again, I have a lot of that sort of trouble with Tezuka's stuff when shrunk down. Might just be incompatible ocular systems.