Surprisingly deep.
I have seen other work of Elffers with just pictures of the food art, but here there is a lot more explanation. Including hints on how to do it, there are comparisons to cloud pictures, ink blots, and the art of Giuseppe Arcimboldo. (The most astonishing is The Vegetable Gardener viewed first one way, and then upside down. Whoa.)
As the book goes over looking for what is already in the food, and what can be enhanced, it encourages not only creativity and fun, but also mindfulness. Also, there is a plug for organic produce, as the irregularities make for more interesting textures.