Sleazy Fork is available in English.
Loads manga chapter into one page in a long strip format, supports switching chapters and works for a variety of sites, minimal script with no dependencies, easy to implement new sites, loads quickly and works on mobile devices through bookmarklet
For some reason the script misses some pages on exhentai, loading a svg-data-url instead of an image.
(This especially seems to happen with longer galleries.)
data:image/svg+xml;charset=utf-8,...