This app was mentioned in 6 comments, with an average of 2.33 upvotes
I bought ComicRack. I've used it extensively last couple of years. Very ugly by todays standards (it's holo still). Sadly, it wasn't updated in 2+ years.
I personally use ComicRack (Free version). It hasn't been updated since 2014, but there are really two features that keep me on it that I haven't found in other readers: It organizes comics automatically into stacks based on the series, and it has auto-scrolling which will scan through the entire page before going to the next one. Most readers I've tried out will only tap into the next page and you'll have to scroll through the page manually. I read either on my phone or Nexus 7 which both have screens too small to really view an entire page in one go so I find the auto-scroll very convenient. Plus I find the library view has that perfect density of information while still showing enough comics at once.
No, American comics police their copyrights and finding a manga scanlation pirate host-like sites are impossible. You can download CBR/CBZ files over P2P, mainly bittorrent and DC++, and weblocker links on 4chan, and read them on an app.
I prefer ComicRack: https://play.google.com/store/apps/details?id=com.cyo.comicrack.viewer
The paid version is worth it if you have big collection and sync with the Windows computer, but the free version works just as well otherwise.
On Android? ComicRack or Challenger, IME.
On Windows? YACReader - being the DEV is seemingly lazy (been blowing off Android port requests for 6+ years!?!) I wish someone would port his iOS version to Android, STAT!
If anyone feels up to the task, here's everything you'll need.