It is well written, one passes from amazement to disgust, laughter to compassion. We discover with astonishment the realities of the French prison system. The story is quite involved, and denounces overcrowding and overuse of "prison guards".
I salute the courage of the author for his "immersion". Also, we must salute his writing talent: he makes us go, we readers, with him in the various prisons where he works, and it is quite enjoyable to be honest.