Summary of technical issues or general flaws in the reader, drawn from some basic usage.
1) The cursor shows "Prev" or "Next" depending on which page you're hovering over. However it's not actually functional in the middle ~50% of the double-page spread. It can say "Next", but clicking won't actually take you to the next page.
Ensure that there's a third cursor state that will be clear that clicking will not cause the current page to change.
2) In single page mode, clicking anywhere on the visible page will not cause movement to either the next or previous page. The activation margins are still out at the ~25%/~75% points of the entire screen/player width.
Virtually all existing web-based readers that work in single-page mode allow clicking on the current page to advance to the next page. Unless you have some specific, UX-based justification for not using that pattern, behavior should be adjusted to match expectations.
3) PgUp and PgDn keys work for moving forward and back in the comic while in normal screen mode, but don't do anything when in full screen mode.
4) Double-clicking on the page does not transition between normal and full screen modes. Note that if you add this, the main page target area in single-page mode should not cause page advancement, but the usable target area for advancing a page should still be extended significantly, and perhaps partially cover the page.
5) There are 10 zoom levels. After accounting for the default zoom, you can click the + button 9 times to reach max zoom.
Based on the aliasing and blurring, it would appear that the 'real' image size is the maximum zoom level, and that it can be shrunk down to the default level. The very small stepping between zoom levels seems somewhat un-useful on the user side, though I could see it being vaguely useful in having steps that allow it to hit significant resolution points for displey. On the user side, though, I can't see much point in having more than perhaps 4 total zoom levels (3 steps from one end to the other).
6) When in full-screen mode, the starting zoom is higher than in normal mode. It only takes 6 clicks (on my computer) to reach the maximum zoom. However I can continue to click the + button, and those extra zoom levels are considered "real" with respect to zooming back out with the - button, up to the maximum of 9.
EG: I click + 6 times to reach max zoom. I click + 3 more times after that, but the zoom doesn't change. However, to zoom back out, I have to click the - button 3 times with no effect, and only on the 4th click does it start to unzoom again.
Anything higher than the normal 9 clicks is ignored. If I click + 15 times, I still only have to click - 4 times to start zooming out again.
Continuing to zoom in on the page within that 7 to 9 click range while in full screen and with the image moved away from purely centered causes the page to shift with each click, even though the page size isn't changing.
7) While it seemed at first that there was no keyboard-accessible means to handle zooming, it seems that it's actually possible: the 5 key (from either the number row or the keypad) will zoom in, while the - key (again, both normal key and keypad) will zoom out.
Overall, that doesn't seem a useful pair. I would instead suggest the - and + keys to make the logical connection with the button icons (and the = key to avoid having to use shift if not using the keypad). There's flexibility for additional controls there, as well, such as using the numpad keys to move the image around, 5 to center, 0 to restore to default zoom, etc.
More keyboard shortcuts: Discovered that F instigates fullscreen mode (still have to use Esc to exit fullscreen). A small overlay that could be brought up to show keyboard shortcuts would be useful. Can add a button, and maybe also bring up with the ? key. It's not a terribly complex system, but easy discoverability is always nice.
8) Hitting the TAB key moves a yellow highlight box around the viewer control buttons. However there doesn't appear to be any way to activate those controls using the keyboard. Space, Enter, and various other keys have no effect.
8a) Using the left and right arrow keys moves the highlight box among the controls, while *simultaneously* changing the visible manga pages.
In my case zoom doesn't work (maybe 2560x1440 resolution is too high), only +-5%. And it would be nice to add vertical scrolling with up and down arrow keys .
Oh, and please add a black background.