There are a few comics I own that are in PDF format. (Some of them I received as a Hugo Award voter, along with a passel of novels and stories in PDF as well; others came from Marvel's DVD-ROM collection of Uncanny X-Men issues.) For these, I'm generally using GoodReader. It's a fine comic reader, and even Marvel's unfortunate decision to save all of the X-Men issues as two-page spreads rather than single pages can be worked around with a little bit of pinching, zooming, and tapping.
Big tablets, small tablets
The original iPad debuted with a 9.7-inch screen, which is close to an ideal size for comics reading. (It's still a tad too small, but it's in the ballpark.) However, the intervening years have seen the release of numerous smaller tablets such as the Kindle Fire, Nexus 7, and iPad mini.
Everyone will have their own take on the ideal device for reading comics. I also know people who read comics on their iPhones, a practice I dropped the day I got my first iPad. Personally, I find any device smaller than the iPad to be less than ideal for reading comics.
I prefer to read comics page by page, more or less replicating the printed page of paper comics. (Maybe this makes me old school, but as long as comics creators are building pages in this shape, I think it's only right that I read them as the creators intended.) Smaller screens require a lot of pinching and zooming, or reliance on Comixology's Guided View to pan and zoom the panels.
It beats not reading comics at all, I guess, but I wouldn't choose it. Even now, when I'm using the iPad mini far more than the original full-sized iPad, I find myself digging out the iPad to read comics. Throw in the much higher resolution of the iPad's Retina display, and it's clear that bigger is better when it comes to reading digital comics.
Though I haven't spent more than a few minutes reading comics on a Windows 8 tablet, a friend who has used it tells me that it's an even better experience than reading on the iPad. Bigger screens make a difference when it comes to reading comics.
Comixology's Comics app on a Surface Pro.
When I first wrote about the state of comics on the iPad in 2010, it was still early days. Since then, the industry has really gotten its act together and embraced the digital version. Most comics are available online the day they're in stores, high-definition files display beautifully on high-resolution tablet displays, and even Marvel's formerly Flash-only subscription service works on iPads now.
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