No worries on responding to your PM, greens. Whether it is "fine" enough to read in the standard vertical / portrait position really depends on the manga / comic you're reading. If the text is large enough, no problem.
Otherwise (as I recommended in the PM), you should consider a 7-10 inch Android tablet, as decent Chinese ones can be had for not a lot of money and there are some excellent CBR / CBZ format reader apps that are available either for free or for reasonably cheap (eg. Moon+ Reader).