This book was a fun read, but it had too many flaws to recommend. Therefore, I will list the flaws first.
#1-I rate this as #1, because it is the most important. This is a children's book. The MC's age is 11. This means children 8 (and probably younger) will read this book. And yet: Before the first third of the book was over, it had used, "arse", "hell", the Lord's name in vain, discussed how Angus (the brownie), was looking at a selkie in her human form completely naked (even if he didn't find it interesting after 150 years, he still watched her), had the child discuss how she knew about sex because it was obviously impossible for her younger sister to "have just happened", and thinks her teacher's husband is a hottie (what 11 yo thinks a 30yo man is hot!?).
#2-Bad grammar. It's "if it were", not "if it was" (this was not in dialogue, and occurred several times), apparently "have mowed" is acceptable, so I'll let that go (must be a regional thing), and it's "none were", not "none was". These should have been corrected, but much like the inappropriate actions, were only found in the first third of the book.
#3-Repetition. The latter third of the book had its own set of problems. Several sentences were repeated, like in the same paragraph even. This happened several times.
#4-The book is written in a jumpy format. It goes: Angus's journal entry, letter to parents from teacher, child's journal entry, Angus's journal entry, letter to family from vet, letter to parents from teacher, child's journal entry, etc. While this is a fun and interesting format, it is confusing, especially at the beginning. A child would have a hard time following it I fear. It would have been better if the family information had been given at a later date, you know, like after the reader actually knows they exist, and maybe even the role they play in the story. It would have also been better to have bigger chunks instead of hopping around all the time. As it is now, why do I care how a vet feels about a cat from a family I know nothing about, not even their names? It's instinctual to skip those parts until they actually matter.
And now for the good parts.
#1-The characters were very well thought out and played. They each had their own personalities and problems, and it showed.
#2-I especially loved how we see Native American fantasy. That is so often skipped over in the fantasy section, and I really enjoyed it.
Final thought-I would not recommend this book to any child for the #1 reason of my flaw section. However, an adult will probably enjoy it a great deal.