For being a skinny book, quite a bit was fit into it.
While none of the color illustrations are new, it's still nice to have a gallery of them. The sketches were also cool to see, and it amazes how much detail is put into something so rough. Oh, and then there's the cover. I absolutely love it. I'm currently caught up with the physical print of the main series, so it's nice to see such a happy/unreserved picture of Myne. I also love how many different items were thrown onto the cover, yet it adds to the fun rather than feeling crowded.
My one complaint illustration-wise is the map of the temple. It's kind of confusing. It does make a bit more sense after reading the short story that accompanies it, but too many details were left off of it. It just seems like an odd choice to leave details off of a map that is supposed to help clarify things.
As for the short story that accompanied said map, it's told from Nicola's POV, and it really does give a lot of insight to the changes going on from Rozemyne becoming the High Bishop and the adopted daughter of the archduke. It's nice to not only get a tour of the temple, but to see how things are changing for Nicola and Monika. Plus, it gives a bit of insight to the blue robe priests and shrine maidens, which the main story really doesn't focus much on.
This is followed by the character design sheets, and I absolutely love this section. It's interesting to see how many designs were spot-on from the first go and to see the tweaks made to others. This sketchy style is really cute, too. The High Bishop's inspiration for his design is quite interesting, considering he's a villain.
Then there's a manga story. Because of how the rest of the book is laid out, it makes this bit a little awkward in that the pages are left-to-right but the panels are right-to-left, but it's not hard to get a hang of. This has a different art style than the main books and the anime, and I assume it's the style used in the manga adaptation (haven't read that yet). The characters have some differences to their designs, the style a little less cutesy, but it still works well. The story was a funny one, and it's nice to see a different perspective to an early event (Gunther's).
This is followed by a long Q&A from the author, though it's a pretty quick read. Some of the questions are ones I know the answer to just from reading past this point in the series, and some questions have been answered in various short stories (I assume some of these questions were asked before the short stories were written/published). Still, there's plenty of new and interesting information, and some answers help to clarify things.
Then there's the questions regarding the author's writing process, and just... wow. She and I are about as opposite as you can get when it comes to our writing processes. As such, it blows my mind how much work she did before she started to write the actual story. It's also interesting that some of my favorite characters were later additions simply because she needed new characters to fill in some of the gaps.
Her writing schedule also sounds insane. I don't see most of this just from the fact I'm reading this series after it's finished (and the only thing to potentially wait on is the physical copies of the English books), but it sounds like she is a highly prolific writer. All her hard work and planning has certainly paid off thus far, though, as it's obvious this series has had a lot of thought put into the worldbuilding.
This fanbook ends with a few bonus comics. I enjoyed them all, but my favorite is 'Seeds.' It's quite hilarious (especially when you first read 'So Much Love').
Overall, there was a lot more to this book than I was expecting, and I love it. I knew from a glance there were the full-color illustrations and some behind the scenes content, but I wasn't expecting the bonus story or the Q&A. It's very clear the author (and illustrator) have put so much heart and soul into this series, and I love learning more about the world and how the series came to be.