I've always loved this book. Exploring Alice's relationship to Makai is something I always enjoy in fanworks, so the focus on Shinki is a delight. The relationship between Alice and Marisa is complicated — and made more complicated still by the current situation — but you can definitely tell how they do care for each other — and you can almost taste how much Marisa misses her own mother (and possibly her mother-figure, Mima) when asking about Alice's.
A while back, ZUN made a comment about his ultimate vision for the Touhou Project, and Gensokyo, in a publishing sense, is to be something like the Cthulhu Mythos. Given the way that the intense and prolific flowering of fanworks has generated a space where we're mostly fine with knowing that each author's Gensokyo may only match another's version in the broadest possible strokes, I think he's pretty much there.