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Title: The Mostly Invisible Boy (#1 Casey Grimes)

Author: A. J. Vanderhorst

Published: 25th of April 2020 (first published)

Format: Digital – 307 pages

Hello Hello! How are you?

I’m back with another book review and #BlogTour organised by Dave from @The_WriteReads for The Mostly Invisible Boy by A. J. Vanderhorst. You know I am a big fan of middle-grade books, especially fantasy, and this one was very unique and I enjoyed it a lot!

Thank you so much to Dave and the author for letting me take part in this tour and for providing me with a free copy of this book in exchange for an honest review. All opinions are my own.


Eleven-year-old Casey is stubbornly friendly, but he’s eternally the new kid at Vintage Woods Middle School. Students look right through him—and they’re not faking. Casey doesn’t know why he’s mostly-invisible, but when he scales a colossal oak, he discovers a fortress in its branches. The forgotten sentry tree marks the border between his safe, suburban life and a fierce frontier.

Casey and his little sister Gloria infiltrate Sylvan Woods, a secret forest society devoted to ancient, wild things. Sky-high footpaths. Survival sewing. Monster control. Shockingly, people here actually see Casey—but being seen isn’t enough. He wants to belong.

Keeping his identity hidden–while struggling to prove he fits–is hard enough, but Butcher Beasts have returned to Sylvan Woods after a hundred years. Trickery is under siege. As the monsters close in, and the fearsome Sylvan Watch hunts Casey down, he and his newfound friends must unearth abandoned magic, buried at the forest’s roots…or be devoured along with everyone else, Sylvans and civilians alike.

A fast-paced middle grade fantasy/adventure book with all the monsters kids could ever hope for.


Trigger warnings: violence, injury, heights (climbing up trees), monsters, kids getting hurt in fights, blood, gore, rot and mould, feeling invisible.

The Mostly Invisible Boy by A. J. Vanderhorst is the first book in the Casey Grimes middle-grade fantasy series in which the main character, Casey Grimes, a young lover of nature discovers a massive tree in the forest behind his house, and a wonderful, scary and enthralling adventure ensues.

When I first heard about this tour, I thought the book sounded really unique, and I wasn’t sure I would really enjoy it, but I ended up having a lot of fun reading it, and I really liked the characters and the plot!


I found the setting of Sylvan Woods to be SO unique. Some people have said that it was a bit like Percy Jackson and while I do see some resemblances, I think it is completely its own thing and I can see Sylvan Woods being a place loved by so many readers. It seems really big and we have only seen a tiny bit of it, so I’m very excited to read more about this place in Casey’s next adventure. 


Casey: Casey is the main character of this book and definitely my favourite. I struggled to like him for the first couple of chapters, but I think it was just a case of me getting used to him, his personality, and his mannerisms. I ended up really enjoying reading about him though. He was kind, caring and wanted to do what was right, despite the situation being totally new and scary. He is really brave and I think through this series he will continue growing and will become a really strong character.  

Gloria: Gloria is Casey’s little sister and she is the cutest EVER. I loved her, she is so sweet and always optimistic. Casey and Gloria have a lovely relationship, it was so sweet to read about and I honestly just loved seeing them be close and work together, along with the other characters.

Luciana: Luciana is the first Sylvan that Gloria and Casey meet and I don’t want to say too much because I think it’s great to read about her through your own eyes (does that make sense)? She was a very interesting character and I really liked seeing their friendship blossom.


Being an invisible child: This is an important part of the book and it is also in the title, but I don’t think we even know why Casey was invisible at school. This is one of the elements that remained a bit confusing to me. I think it was kind of the entry into Sylvan Woods in a way, but I’m still a bit unsure. I thought it was a very interesting premise though, and I’m hoping I get answers to my questions in the second book.

Nature, woods, trees: I love books set in nature, forests, natural places with lots of trees and plants and I love that the “town” or should I say community and school are set in the woods. I think this was unique and I definitely think it does echo the setting in the Percy Jackson books, but it also completely different. I liked this setting a lot and I can’t wait to discover more places in Sylvan Woods!

Friendship: As Casey has felt invisible for such a long time, he actually doesn’t have any friends, so when he arrives in Sylvan Woods and becomes friends with Luci, it is a completely new experience for him. One thing I love to read about, especially in middle-grade books, is friendship. I really liked seeing Casey, Gloria and Luciana’s relationship blossom and eventually include more characters.

Adventure, magic and missions: You know I’m a fan of magic in books, and this one, while the magic side has not been fully developed yet, I did enjoy and I know that we will find out more about it all soon. I love adventures and missions and I thought that this book, while it is quite short, does pack a punch. Lots of things happen and it’s all very action-packed, so the pacing was fast and flowed well and I just really enjoyed this plot!

An intriguing and unique new MG fantasy series: Finally, I think this is a great, unique and new take on middle-grade fantasy. I feel like MG fantasy is among the most unique in the overall fantasy genre, and I love reading new stories and plots. This one did not disappoint, I was enthralled throughout my reading of the book, and I think I could have read it easily in one session, had I not kept falling asleep (nothing to do with the book at all, work took it out of me this week)!! I am definitely going to continue this series, I just need to get my hands on the second book!!


Overall, I enjoyed reading this book a lot. I do have a few questions and maybe some confusions because the story did jump about a little bit at times, or characters would say things that didn’t make sense, but that was only very rarely and I can hardly remember the places where I was confused. I think it is a really strong first instalment in a series that I know I’ll enjoy a lot.

The writing style was also really nice and fluid. As I mentioned, there were a few jumps and a few little places where I felt something was missing, but overall, both the writing style and the pace were good. I found that the story and plot were well-executed, and I’m sure it will get stronger in the next book as well.

I gave this book 4 stars (full ASPECTS rating below). It was a very enjoyable first book in a middle-grade fantasy series, it has a lot of potential and I can see this becoming a popular series.

If you love unique and fun middle-grade fantasy stories with great and interesting characters, a cute little sister you can’t help but love, a forest setting with a school and “magical” community, lots of secrets and things just waiting to be revealed, monsters, missions and bravery… this is the book for you. I guarantee you’ll not be disappointed. I highly recommend The Mostly Invisible Boy to fans of middle-grade books, but also to readers of all ages!

That’s all for now, I hope you enjoyed reading this post, see you soon, stay safe,

Ellie xx


AJ Vanderhorst has had many jobs, including journalist, paramedic, escape artist, and baby whisperer. One time in fifth grade, he built a traffic-stopping fort in a huge oak tree, using only branches and imagination, and slept there for a week.

Now he and his wife live in a woodsy house with their proteges and a ridiculous number of pets, including a turtle with a taste for human toes. This makes AJ an expert on wild, dangerous things—invisibility spells, butcher beasts, hungry kids, you get the idea.

He is the only author in the world who enjoys pickup basketball and enormous bonfires, preferably not at the same time. He and his family have drawn up several blueprints for their future tree castle.

A.J.’s Links: WebsiteGoodreadsTwitterAmazonFacebookInstagram


Atmosphere – 7

Start – 5.5

Pacing – 6

Ending – 7.5

Characters – 6.5

Theme – 6.5

Style – 7.5

Total = 46.5

This list includes some affiliate links. If you decide to purchase a book from one of my links, I may earn a small commission, at no extra cost to you.

If you would like to purchase this book, you can find it here: Amazon UKAmazon FRAmazon USAbeBooksThe Book DepositoryWaterstonesBarnes and NobleScrib’dBlackwell’sBetterWorldBooksWordery


  1. This sounds like a great mid-grade fantasy series. I’m so glad you enjoyed it!

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