Say one wanted to develop an e-reader with something different than the current e-readers have on tablets. This e-reader would need to have a store where books can be purchased from.

If I wanted to sell existing novels on this platform, let's use George R Martin's books which are of course quite famous. What legal steps and resources will I need to use to be able to get to the position I can sell these books on my platform.

What legal steps

Consult a lawyer. Depends very much on your location.

"Consult a lawyer"

I would if I had the funds a lawyer usually demands :(

Here, when starting a business there are resources to help you get started (chamber of commerce). Perhaps where you are too. The problem with advise you get here (on the forum) is that it's unlikely to be applicable to your situation for 100% (unlike advise from a lawyer).

:O You mean I can chose my area, call them and ask them all the legal advice I need and for free?

There has got to be a catch.

the most logical thing to do would be to ask the publishers... Which is what a lawyer would tell you too.
Without permission from the publisher you're not going to legally sell anything.

That's quite apart from all the legal stuff you need to handle to set up a company in the first place, you need a lawyer for that.
Just because you don't have money doesn't mean you're going to be able to get away with inadvertently breaking the law because you failed to get proper legal advise.
And that's as true of Derbyshire as it is of Berlin or Sao Paolo.

Of course. By no means was I using my city as a means of saying it's ok to sell stuff illegally, but you have answered my question in that I need the publisher's consent.

Just so I can reanalyze my plan. Would you say a publisher is likely to accept allowing their material to be sold by on a web portal someone has created to sell books, but the person running this web portal takes, say, 15% profit from each sale made. Surely the answer most publishers would give is yes right? What do they have to lose?

no, the answer will be NO. They have a lot to lose, not in the least the exclusive (or semi-exclusive) contracts they already have with Amazon, BN/Bol, and Apple, each of which sell more copies per day than you'd sell in a year.