iPhone or Another iOS Device with 4-6" Would Be Easier for Reading

I'm read a couple of books in the iPhone now.  iBooks and Nook app.  I'm considering getting the Barnes and Noble Nook reader because I like having a bigger screen to read a book with.  It has nothing to do with the e-ink.

In fact, I find the e-ink a bit dated.  It's slow and I'm just not used to the touch function on these dedicated readers.  Rather, I should say the lack of touch in the readers.

So, would I have liked the iPhone 4S to have a 4" screen?  Sure.  It means bigger fonts or you can fit more text into one page.

But should Apple release a device with around 6" +/- 1", Apple could end up locking up the reader market rather quickly.  In previous posts about the tablets and screen sizes, we always focused on productivity rather than consumption.

What do you think?  Would get an iOS device with 4-6" just for reading?