I really like the way the author Catherine Fisher writes. A blend between Madeline L'Engle, J.K. Rowling, and Cornelia Funke, her style is incredible. I was looking up the release date for my favorite series of hers - the Chronoptika series - and I found out that the 4th book in the quartet had already been published. It is called 'The Speed of Darkness', and it is the conclusion to the group. The first book is called 'Obsidian Mirror', and it is AMAZING. Please look into the novels; they're a great read.
Here is the cover of 'The Speed of Darkness'.
Here are all of the other covers in the series; be on the lookout for them!
The books were originally published like this, with 'The Box of Red Brocade' being republished as 'The Slanted Worlds' later on.
Here is a picture of the original cover for 'The Slanted Worlds':