The best part about ZUN's books are the prologue and epilogue (if those are the right words). Same with this one.
Interesting thing is, half the people who read that book really can't read the kanji in it. No one knows to read 役小角 as えんのおづぬ. That particular example has furiganas in the passage, but most others don't. Pretty severe Japanese.
I like Koishi's spellcards, because they have to do with mental philosophy.
For looks, I'd say Eirin's Tenmou Chimou Hochou no Hou(天網蜘網捕蝶の法).
お遊びで見せて貰ったスペルカード。
完全に自由を奪う。何処にいても自由が奪われてしまうとは恐ろしい。
実際は動けないだけで難しくはないが、これでお遊びだというから精神的に負けた気分になる。
あれぐらいマスタースパークが沢山出せればいいんだけどな。
Translation:
A spellcard she showed me for leisure.
It completely steals your freedom. To lose movement no matter where you are is quite frightening.
In actuality, it's just that you can't move, so it's not that hard. However, she says this is just for leisure, so it makes you feel like you lost.
If only I could shoot that many Master Sparks.
I'm so bored, I could translate this whole book. But I'm too bored to do that.