This book is an action-packed, time-traveling, murder-filled, sci-fi drama. This might sound unbelievable and even devilish, but it's true. Read it, but don't read it alone at night! If you are alone, then read it to your pet.

The main three characters in this story are Riley, aged 14, Chevie, aged 17, and Garrick, very old. Riley and Chevie are two friends who meet when Riley, who is Victorian, time travels via pod to get as far away as possible from Garrick the assassin.

Horribly, Garrick also travels in time to hunt for Riley – so Riley has a huge amount of obstacles to deal with, all the while juggling life between the 21st century and the Victorian era. How will he cope?

This book is for a bright 10 year-old, though really tweens or teenagers unless you are Matilda herself. It's quite a complicated read, so definitely not for under 10s.

One of us had to drag herself through reading it, but once you've started there's no way out! There are a lot of complicated parts to it. We are all good readers but there was a lot we didn't understand at first and often had to go back and re-read bits – but this challenge made it more interesting.

The book is so intriguing that it near to impossible to be able to dip in and out of it, you need to be able to dedicate a lot of time and concentration to it. Some of us find it best to read it in the bath since some of us have young siblings and it's hard to get away from them for long enough.

It's pretty much the scariest and definitely the thickest book we've ever read.

We have a few complaints: first of all the front cover doesn't look very appealing for girls and yet one of the main characters Chevvie is a girl. She's not on the front cover. She should be! The girls in our group wouldn't have picked this book up in a bookshop no matter how tomboy they were because it looks like a boys' book. But it isn't really!

Second we wished the chapters could be shorter because sometimes we thought, "Let us just finish the chapter," but was never ending! It's confusing to come back to a book like this after a day or two mid-chapter.

The book could do with some illustrations to help the mind imagine what that pod actually looks like and to keep us focused. and we would love to see what the author thought Garrick looked like.

Out of 10 we'd give it 8.5. A brilliantly thrilling read, that stretches your mind.

• Buy this book at the Guardian Bookshop

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