I don't do a lot of reviews, but I wanted to add my opinion for this book.
I am huge into races with any RPG that I run. I love having something new to introduce as NPCs with either as races or as classes, sometimes both. The moment I saw this book, I was intregued. I'm glad I grabbed it.
First, the races in here are all well thought out. As per the ARG, they are a little "heavy" on racial abilities, but that isn't always a bad thing. This more particular in races that you already explained as "rare", as per the title of the book. Odds are, you're not going to have entire nations of these races running through your typical campaign world.
I enjoyed the presentation, though the "handwritten text" was a little difficult on the eyes, sometimes, when reading these before turning in for the night. (Yes, I read RPG books like some people read novels, before going to sleep.) That was my only complaint format wise.
I like that each race had an interesting backstory, as well as an "iconic", with multiple level breakdowns. It would make it easy to introduce one of these characters as a recurring NPC. The fact that some of these stories are intertwined is a nice touch. It kept me interested in seeing who was tied to whom, as I progressed through the races. "Ooo.... so this character is the character mentioned... indeed.... hmmm... Interesting."
My favorite races from this book are:
Isoonia - Eel/hagfish people that are pretty. Nice.
Khartajan - Arabian Unicorn People. Another interesting, well described and thought out race. A great flavor race to add to an Al-Qadim or similar setting.
Leimaxi - Long armed abomination folk. Just so... alien looking and abilities, I feel a little in love with the race as a whole. I love the "stretch armstrong" ability that the race has.
Morphling - Doppleganger/mongrolfolk half-breeds. I do like these, shapeshifter races are another fun race to add to almost any game. Only a little thrown off by their one racial ability/penalty to change shape involentarily when in specific situations. While I think I understand the intent behind the ability, the ability seems more helpful then a concern. I think I would of added more "penalty" changes, with no real game play effect, but that would be me, and I've been told that I can sometimes be a bit of a jerk when it comes to "rod of wonder"-like lists.
Verechelen - Dinosaur Lizard Men. I really like the flavor and appearance of these as well. Just greatly thought out and designed.
One race I wasn't sure of stats matching description was the Kaalogii. There's a lot of description about them being subservient, confused, and impulsive, but the stats of a bonus to Wisdom, negative to Charisma didn't seem to match in my mind.
All in all, this is a great book for, what appears to be, a first outing. I'm really impressed. I gave it a 4 out of 5 because of some mild issues with the formating, a few typos, and some minor flavor/design concerns, but all in all, a great addition to your Pathfinder library. I look forward to more books from this company, in the future.
I also can assure you, in my next campaign, there's going to be a few more "rare" races that the PCs are going to stumble upon, as the game progresses.