Looks like they're releasing random comic stories together as collections. Apparently a similar thing is done with the Sonic comics, and of course similar things have been done with Archie. This first collection has the Rainbow Dash and Fluttershy micro series issues, and the Rainbow/Trixie Friends Forever issue. I'm guessing this is basically for super completionists and parents who don't know better, but it has new cover art.
Archie produces a lot of different types of collections in order to hit a broad array of distribution channels (comic books, magazines, digests, and trade paperbacks) and shelf space for maximum exposure. Not... really sure what IDW thinks they're going to accomplish with hardbacks, but there's probably some specific market segment they're trying to hit that the existing trades don't.