Like Frederik says in an interview with the Guardian:
"Words are very precise whereas, with images, you can project a lot of yourself on to them. A person can invest their own emotions in an image, like a mirror. People related to this book in different ways."Fred's story is not so common-place and it encompasses myriad emotions - from love to anxiety to terror to neurotic self-analysis to surreal moments (talking to his alter-ego in the form of a poetry quote spouting mammoth!). Perhaps it is only through pictures that a person can convey all this without getting melodramatic and sentimental. That may be the charm of graphic novels; especially for a certain kind of poignant and angst-ridden story, since it allows the reader to enter a world where not much is said and a lot conveyed.
Another French graphic novel I read last year - Ordinary Victories by Manu Larcenet - was also a very satisfying read. The author portrayed angst and neurosis - the kind that you wake up from sweating and which keeps you up all night - very well. Like great French directors like Godard and Truffaut, France has some budding artistes in the graphic novel genre, who know how to perfectly execute their art to provide us a with poignant and emotion-laden slice of life, without getting overtly melodramatic or sentimental.
P.S. To understand what the "white rhino" is all about, you'll have to read the book.