I'm gonna try not to misquote anything here. I think I read that RUE, although it is a publishing company, bares the Excelsior emblem because Excelsior approves of the textbooks that Rue uses, as opposed to other publishing companies that develops study guides with Q&A chapters that contain very little teaching content, the latter part of this statement being my personal opinion.
Although I've never used Rue and I think that it would have been cheaper to use EC books, I believe you will be okay with those books because I found the information about Rue textbooks from the EC website a couple of years ago. They've since changed the website around so I can't say how to go about locating that information now. Just be sure to follow the EC examination content guide to cater your studying with the Rue books and you will fair well. Good luck!!!!