I just started to use it, but already really love Readium, this app is definitely the best available reader for Chrome OS. There are two things I miss. One thing is the line spacing. I have books where the lines ranging from double spacing to almost zero. It is very uncomfortable to read with too tight lines, also rather weird to read with huge line spacing. Unfortunately there is no option to set it. Is there a way I'm not aware of? Or is there a way to request this feature? Because I think this is (should be) really a basic option.
The other thing is that when I added my books to the app, they will appear in that order, and can't sort them in let's say, by title... therefore at times it could be difficult to find the book I want to open. This is a small inconvenience.