Be sure to check all the pages your epubs on a number of devices. They do not respond all the same. Drop caps, if you use them, can be a problem for some devices. Invisible page numbers, if you use them, can show up as unexplained blanks on some devices.
Three Men In A Boat is an epub in the library on MR. It has formatting which works on many devices and you might examine it for how fancy formatting can accomplished successfully.