Reasily

Open multiple books simultaneously as if they are different apps. You can switch between opened books and the book list with the "recent apps" button of your device.
Swipe left/right to go to next/previous chapter or page.
Table of contents is in drawer menu.
Display options: sepia/night theme, custom font, margins and line-height adjustment, text justification, popup footnote position.
Scale text size with fingers (pinch-zoom gesture).
Click image to enlarge it and show its description. Scale image with fingers.
On Android 7 and above, you can read books in float windows or split views.