I just checked about this Mangle Viewer and apparently it hasn't been updated since 2010? So it sure doesn't work on a current Kindle. Have you tried
KOReader? I've had it installed since I jailbroken my Kindle PW4 (10 gen) but I've only just tried to use it to read manga now. The result is quite decent using .cbz files (folders with manga images, all compressed in .zip). The following settings on the bottom bar are necessary for better viewing:
1. "Fit" to "Full".
2. "View Mode" to "page".
3. "Dewatermark" to "on".
You can make each of these settings default by long pressing on them.