The "Star Ratings" on Goodreads for this book look exactly like a standard Bell Curve -- the Apex is at 3 Stars, with the low end tapering (as Bell Curves do) off to 1 Star, and the high end tapering off to a 5 Star review.
I totally understand the 1, 2 and 3 Star reviews. Do not ask me why on earth the 4 and 5 Star reviewers were so generous -- I hope their reviews speak for themselves and tell us "why."
If a reader expects this book to spell out exactly what the philosophy of Existentialism entails, that reader will be sadly disappointed and will favor a 1 or 2 Star review. Likewise, if a reader expected a primer on what precursor philosophical movements inspired Existentialism, nope. Again -- either a 1 or 2 Star rating.
If a reader expected a biographical tale explaining how the events of the lives of Jean-Paul Sartre and Simone de Beauvoir intersected and became an intertwined love affair; and how this intertwined relationship proved to be the birthplace of the tenets of Existentialism, and how their shared experience influenced their very different writings grounded in Existentialism, well . . . forget that too. 1 Star.
So, why give this maddening little book 3 Stars? If one simply views it as a superficial slice of life of a group of intelligent French writers living in Paris, and gathering in cafés to smoke, write, drink, eat and discuss -- often argue about -- politics, WWI, WWII, music, cultural trends (and the philosophical approach to making sense of it all), it holds together nicely and serves as a sociological study of the Parisian café life of the 1930s and 1940s and a fragmentary biographical sketch of some of the main writers in the group (primarily Sarte, de Beauvoir, and Camus, etc).
This book is the Existential 1930-40s version of the 1920s "slice of life story" recounted by Hemingway's "A Moveable Feast" (Hemingway's recollections of the life and times of the American "Lost Generation" of writers (namely, the expats Gertrude Stein, F. Scott Fitzgerald, and Hemingway)) who lived in Paris to write and think. If a reader approaches the book within this framework, then the reader should be somewhat pleased by the graphic novel's approach and content.
In fact, this reviewer recommends the reader to broaden the experience of this graphic novel by reading it in connection with author Sarah Bakewell's fantastic non-fiction introduction to existentialism, Sartre, and de Beauvoir, "At the Existentialist Café: Freedom, Being, and Apricot Cocktails." Bakewell provides all the things that a reader could have reasonably anticipated to be included in the graphic novel, but were clearly left out -- for a reason. The graphic novel is a carefree, fictionalized overview of the daily life and times of Sartre and his colleagues. It is a period piece. In contrast, Bakewell's "At the Existentialist Café" is a factual biographical portrait of Sartre, de Beauvoir, Heidegger, Husserl (and the others) AND a great primer on Existentialism as a philosophical school of thought.