This app is utterly non-functional. Purchase it at your peril. I have only a modest collection of ePub books, 23 in total. They are all DRM-free and are all completely readable within iBooks. Nearly half of them are completely unreadable within Scarlett. As just one example, my copy of The Wise Man's Fear by Patrick Rothfuss, which works flawlessly on both my iPad and my iPhone within iBooks, displays nothing but a chapter list and blank pages when I load it into Scarlett. A search of the book for "Kvothe" (the name of the main character) provides a list of results, but clicking on any of those results to actually view them reveals only more blank pages. As another example, Tom Clancy's Rainbow Six manages to display the book's title and a chapter list, but nothing else beyond that. Yet another example, Neal Stephenson's Anathem can't even display a chapter list, it merely shows a list of the *sections* of the book, and no text. Those books that do work function competently enough, but if the ratio of working to non-working files in my collection is at all representative, the odds are not in your favor. If you actually want to use an app for reading ePubs on your Mac, do not buy this app. It does not work as advertised.
Excellent ePub reader
I found Scarlett to be one of the best ePub readers I could find. I enjoyed the ease of use, the great rendering engine, and the customization in TTS. The only things that could make this better are configurable gestures, continuous reading support, and bookmarks