First I read the book, written by Greg van Eekhout. I had to visually create the characters and develop them so that I could make a cover and some drawings for the interiors. The characters already had descriptions in the book, so following that briefing I stated to test and sketch. This is Ada, the secondary character.

Same with the main character, Cog.

There is also Trashbot, here's a bunch of little sketches

Then I compiled my favourites in order to start making choices and also to present them.

Here's the version I liked the most of all of them.

Some clean ups ready to use for the interiors!

I think this one is my favourite. Also a clean up for the interior.

More clean ups for interiors.

Then I had to look for the right cover. I had a great briefing from the art department at Harper Collins, so it was a lot of fun to explore with that.

This is the final sketch we went for.

I always like doing color tests when I work, this was the one I liked the most for this cover. They liked it too, so we went for it! :) 

And this is the final cover