I have mixed feelings about this book.
Putting on my "everyone's a critic" hat... The pacing builds incrementally over the course of the novel. It felt slow in the first half, and I didn't reach the "can't put it down" stage until two-thirds along. I hate diaries as a narrative tool, except in small doses. I don't have patience for the daily drivel that would make a diary more authentic, but get annoyed when a "diary" comes across as a well-crafted, first-person narrative written by an author rather than by the diarist. (Though, to be fair, Walton strikes a good balance between those two pitfalls.) I can see, from the reviews of the book that I've read, how one might feel the ending is abrupt, or that the portrayal of Mor's mother is two dimensional and cliche. The book can also come across as being more about the way an individual can lose themselves in books, can escape into their imagination, than about the realities of finding oneself, and one's place in the world, by way of fiction.
I love this book, and it took me two-thirds of the account to get to know Mor well enough. Yes, all of the criticisms above can be leveled at the book. But I never felt, at any point in the book, that the way it was written was anything less than necessary. This is a book about a year of transitions, of crossing thresholds both social and soulful, of being between, of being an Other among Others, both fairy and human. This is a realist novel, with the most accurate portrayal of the magical that I've ever read. (Please note that I am not saying "most accurate representation of the fantastic"; the fantastic is not synonymous with the magical.)
It is both unflinching and sympathetic in the way it shows how imagination shapes experience. It allows one to speculate about the reality of Mor's experience *without* breaking the enchantment of that experience. A reader can question whether Mor is just believing in make-believe, is escaping into her imagination - and in Mor's worries about the effects and extent of the magic she's done, it is clear to the reader that she's skirting delusion. Yet, at the same time, Mor's experience is real to others around her (e.g. the walking stick and Wim seeing the fairies). The way she perceives magic in objects (e.g. the earrings) and in the intent of others (e.g. her father's sisters) is accurate - even if a skeptical reader would interpret her perceptions as an intuitive understanding of psychology, rather than "magic" as such.
This book doesn't say to the reader: "If fairies and magic were real, then..." Rather, it says: "Fairies and magic are real, and..." It doesn't assume a particular objective reality and make an exception to that authoritative assumption. It assumes experience is subjective and reality no more than the interaction between perception and imagination--both our own and with others' perceptions and imagination.
And then there's my personal stakes in the book. I put off reading it for a few years because, within the first few pages, I could tell I'd need to prepare myself for it. There are too many touchstones.
Everything Mor says about magic, from the way it works to its deniability, matches my own experience. I've never read any account, fiction or non-fiction, that does that (though I must admit I've never seen fairies or ghosts - though, maybe will-o'-the-wisps).
Books, and speculative fiction especially, shaped my growing years in very similar ways. I know what it's like to grow up without a father, living with a mad mother, and much later find out you're more like the distant father. I know what it's like wanting your childhood back, being forever marked by survival, longing to belong.
I've never read of, nor spoken with, anyone who shares my experience of trains and travel as times of safety, contentment, and connection - aside from Mor's comments on the same. Those times of transition are a comfort because being between feels right, instead of wrong.
I know what it's like to live with chronic pain and to endure limited mobility, to always be the outsider looking in (and questioning one's right to belong once on the inside). And I've experienced the same moments of interconnection that Mor does near the end of the book. One of the most powerful being when I was on the train out from Aber, at the end of my semester in Wales, watching the sun light up the low hanging clouds drifting down from the mountain tops.