The Prohibited Sketchbook, published a year after Volume 3, provides a rare insight into Luis Royo’s creative process, containing numerous examples of preliminary sketches and studies for the images in the Prohibited series. Pencil sketches, ink drawings and loosely-coloured studies show how he builds his ideas and compositions. The only criticism of the book is that too often images overlap each other, which detracts rather from the integrity of some of the more complex drawings.