Ranked in these QuestionsQuestion Ranking
Pro Supports many formats
Supported formats include: Adobe PDF (.pdf), Microsoft Word (.doc, .docx), Microsoft PowerPoint (.ppt, .pptx), Plain and Rich text (.txt, .rtf), EPUB books (.epub), OpenDocument (.odt, .odp), DAISY books (.zip)
Pro Desktop and Web versions
You can use it on any internet enabled device. It also has both Mac and Windows applications.
Con Subscription service
$1.99 / month or 9.99 / 6 months.
Con No desktop version for the mac
Only available as full native apps for iOS and Windows, otherwise it's desktop browser and bookmarklets.