Reddit reviews Fairyopolis: A Flower Fairies Journal

There's also a wizard one (blue), a monster one (green), and iirc an Egypt one (gold).

Edit: I think the fairy one had a slightly different naming convention (not an -ology). Maybe Fairyopolis?

Only thing I can think of is Fairyopolis, it’s a large, purple, hardcover book. But I wouldn’t consider it thin by any means. Here’s an amazon link to see the cover of the book. Hope this is it.

Ahem, WELL, this may not be quite up your alley, but I find these kind of "adult pop-up books" really cool. This is a fairy one- It is in the form of a "pseudo-journal":
http://www.amazon.com/Fairyopolis-Fairies-Journal-Glen-Bird/dp/0723257248/ref=sr_1_9?s=books&ie=UTF8&qid=1395018269&sr=1-9&keywords=fairy+book



There is also the Wicked Lovely series- it deals with the Summer Court and the Winter Court.

I second the OR Melling books. I loved them at 12-16 years old. I ALSO second Holly Black! Good YA books. :)