TS: Imagine the adventures of the heroine/author of this book and how her group succeeded under her leadership.
You see, Rose reminds you of yourself. It's not just that purple appears to have been her thematic color, it's also her intelligence, curiosity, and so forth. But she doesn't remind you of yourself today. She reminds you of yourself at Canterlot, before you came to Ponyville, back when you were too busy studying to go to Moondancer's parties or just to notice that other ponies cared about you. That's what you see in this author. You see somepony who still wonders -- or perhaps has given up wondering -- what friendship could be. Somepony who treats her friends as means to an end, even though she herself doesn't really know what that end is. Life, and Princess Celestia, gave you a second chance, but you don't think Rose ever got that. She had to enter the "Medium" too soon.
At the end of the book -- you confess you skipped to the end, you haven't read it all yet -- Rose explains that she is going rogue. She has blown up a "gate," and she is done playing by the rules of the game. She doesn't seem to have consulted her other players about this at all. Well, you've been in a situation like that yourself, when you thought Discord had hidden the Elements of Harmony in the hedge maze in Canterlot. And when Rainbow Dash broke the rules of that game and took off by herself, it took all five of you to get her back and save the day. You don't think Rose would have helped with that, and that's why you don't think she's a good leader. Which, of course, makes everything else she says in the book somewhat suspect, but that's an entirely different kettle of fish.
The book's postscript is "magic is real." Your time in Ponyville has taught you that the real core of magic is friendship. And if Rose was only just finding out about magic... she must have had a long way to go in everything else.
Ponies rendered in General Zoi's pony creator