It is possible perhaps to classify areas of experience and thought into various regions such as epistemology, and also to classify philosophical realms of experiences and thought about the extended phenomenon of experience as physical cosmology or even metaphysics, yet obviously all experience even of astrophysics and speculations about M-Theory are personally, subjectively experienced if at all.
Instead of debating about the reality of other minds, or conjecturing about the ultimate nature of matter and experience such as in realist schools of thought versus idealist Sartre simply described what is was actually experienced phenomenally for-himself.
Later of course Sartre went beyond his tome ‘Being and Nothingness’ and 15 years later published the 1000 page approx. “Critique of Dialectical Reason’. Whereas the first, rather revolutionary philosophical work reaching popular scales of the 20th century (I’m excluding technical philosophical works or even ‘philosophical’ works such as Einstein’s pieces on special and general relativity) essentially examined personal subjective experience and the words or terms used to describe the subjective phenomenology of mind were elaborated, in the second work Sartre described social levels of individual experience within a collective setting. The book is not a socialist polemic of course; rather it describes how subjective minds interact in settings such as an automobile factory. As far as sequels to brilliant works go, it is not a disappointing effort at all.
Sartre’s fiction works such as the freedom novels are quite good too. One should not underestimate the quality of J.P. Sartre’s fiction…it’s quite brilliant. Yet if one wants to discover a period novel equal to Dostoyevsky’s ‘Brothers Karamazov’ or perhaps ‘The Idiot’ (especially useful with recent U.S. administration tendencies toward neo-corporatism) I recommend Stendhal’s book ‘The Red and the Black’. The ‘Red and the Black’ is perhaps like ‘Crime and Punishment’ with a more sensational ending…it should be recollected that ‘Crime and Punishment’, while an excellent psychological novel, is more of an incitement of Tsarist structured poverty and conditions that led poor would-be college graduates to perpetrate senseless crimes for profit than it is about Russian criminal phenomena and the corrections system of the era. One might expect ‘Crime and Punishment’ to be something like Solzhenitsyn’s ‘Gulag Archipelago’ but of course it isn’t. I believe that Dostoyevsky’s major contribution isn’t to a philosophical movement of existentialism but to the art of literature and omniscient narrative.