Tanya's a girl with a secret - she can see fairies. But these aren't the type of fairies who grant all your wishes and make your dreams come true - they're the type who play tricks on you and get you into trouble with your mum!
Her 'gift' sees her sent to stay with her grandmother for the summer where she has to dodge the grumpy caretaker and slowly becomes good friends with his inquisitive son Fabian.
Tanya's lived her whole life with fairies playing tricks on her, but it makes life hard when no-one else can see what they're up to.
When Tanya's mum get's tired of her seemingly crazy behaviour, which is nearly always caused by the fairies, she sends her to stay with her grandma.
During her stay, while trying to keep the fairies at bay, Tanya discovers an unsolved mystery about a girl who vanished in the woods 50 years ago - someone her grandma refuses to talk about.
Fabian, the caretaker's son, is also bothered by the girl's disappearance as his ageing granddad was the last person to see her alive and loads of people think he had something to do with her going missing.
As Tanya and Fabian try to unravel the mystery they end up in real danger, but will the fairies who followed Tanya to the mansion help or just make matters worse?
The idea that fairies are all around us, but we just can't see them, is one that's hard to get out of your head.
The tricks some of them get up to are a nightmare for Tanya, but make for great reading!
There aren't really any weak bits, but if you're easily scared this might be one to read when you're a bit older as tales of the fairies' dark side can be pretty sinister at times.
Absolutely - it's a real page-turner. It mixes magic and fairies with family and friendship into a dark and sinister tale that will keep you hooked until the very last page.
This reviews page is now closed. Here are some of the reviews you sent in.
"I suggest this book for 9 to 16 year olds. It is a superb book. The storyline is mysterious and just when you think one thing has happened you're going to have to change your mind. Read now!!"
Alexandra, 11, UK
"I am reading this book at school at the moment and have been for a while now. At first I thought it was a bit dreary and I couldn't really get in to it. I decided that it was just because I was reading it at school and couldn't concentrate on it well. Doubt hung in my mind until about chapter ten and then it really started getting good. I have been hooked ever since and have even been trying to read it in lessons! I find Tanya easy to relate to and the story is gripping but not confusing. Some bits are a bit gross but I don't mind. I want to carry on reading it forever!"
Frankie, 10, Norwich, England
"It is such a good book! I really enjoyed it. It was full of mystery and adventure!"
Kate, 10, London, England
"I think The 13 Treasures is an excellent book. I read it around February or March for the first time and I made the mistake of reading the scariest part (well I think it's the scariest part). It's where Tanya and Fabian go into the nursery and hear the fairy talking about bad things that have happened. It's a real page turner - I stayed up until two in the morning reading because I just couldn't put it down! That's true! Red was my favourite character because she's just really cool. I advise you strongly to read it. Trust me - I own it. My friend Emily, who I lent it to, agrees with me."
Isabella, 9, Suffolk, England
"I thought it was really good. I bought it and have read it five times already. I have never read a book that is so good. Michelle Harrison you ROCK!"
Amie, 12, Birmingham, England
"It was fantastic but a tiny bit scary. My fave character was Red."
Rebecca, 10, Kent, England
"I love it. It's great. The best ever!"
Kayleigh, 9, Oxfordshire, England
"I am reading this book right now and it's amazing! Michelle Harrison is FAB!"
Claudia, 11, Cheshire, England
"I love this book so far - I am reading it at the moment! What is really good is that there are two parts to the book, so if you want a change of book for a while you could always come back to it later. If you are into mystery or fantasy this is definitely the book for you!"
Maddy, 12, Hertfordshire, England
"This is a brilliant book! I could not put it down. The plot is full of twists and turns, there are surprises around every corner. The book is rather dark though, I would not recommend it to young or easily scared children. Five stars!"
Rhiannon, 10, Scotland
"I got this book a couple of weeks ago and I have never had my nose in a book for so long!"
Nina, 11, Swindon, England
"WOW! This is a great book - full of quirky stuff! If you have to get a book get this one. It's brilliant!"
Sophie, 10, London, England
"I've just read the prologue and it has already got me hooked!!!"
Becca, 13, Kent, England
"I totally hate this book - it's not my kind of reading!"
Annalise, 10, Kent, England
"I've read a small amount of this book and I think it's really good. I couldn't put it down - well, I had to when I left the library!"
Megan, 11, UK
"I think this book is an absolute cracker."
Charlotte, 13, Liverpool, England
"This is the greatest book ever! She's a really good writer and she says that she is going to be writing a sequel - I can't wait!"
Florence, 12, Kent, England
"I love that book. It's really cool and adventurous - I just love it!"
Charlotte, 13, Derbyshire, England
"This book rules the world. I love it."
Mark, 12, Manchester, England