Wow, props to you both! I'm the resident tech support for my household, and it can get a little frustrating at times.
I like CoolReader, and also FBReader. FBReader doesn't leave the icons on the screen, but it's more compatible with Calibre metadata (or possibly I haven't found the right settings in CoolReader yet). In FBreader I can find a book by tag, series, author, title, genre and the filesystem. In CoolReader, I can only see how to find a book by title or author. FBReader also has much clearer settings and it's easier to change it between Night/Day mode than CoolReader. CoolReader can display books more nicely, but it's not as easy to use as FBReader I find.