It's more like a sketchbook actually. It has all the character sketches and layouts for the comic panels. The sketches are nice. There are also some work-in-progress panels that show you how the sketches are turned into the final ink and coloured version.
The book also has some guest artist contributions, each with a full page illustration for the characters in Brigada
You can check out more art at the artist Enrique Fernandez's website at https://www.enrique-fernandez.com/