Okular is great for epubs in that it can show them as a single document whereas most programs break them in to chapters that can't be searched across. However,

Okular is great for epubs in that it can show them as a single document whereas most programs break them in to chapters that can't be searched across. However, it can also be terribly slow on some epub files even on a fast PC [0]. It also has problems rendering some files that other readers like epubreader have no problem with. [0] https://bugs.kde.org/show_bug.cgi?id=359932 https://bugs.kde.org/show_bug.cgi?id=359932