Qohelet (Ecclesiastes) is an observatory lament of the absurdity of this life, promoting a resignation -- albeit not negatively -- to having no control over one's own existence or destiny and an enjoyment of the pleasures of life (which G-d and G-d alone is responsible for having provided) while steadfastly upholding and fulfilling the commandments of G-d.
(Note: all work is futile, as G-d either will or will not provide, but enjoying that which G-d does provide is necessary and it seems all there is. Also, man's destiny is not in his own hands, but in those of G-d, whether man is wicked or foolish or full of wisdom, so dwelling is perhaps a folly, but rather we should live as simply as possible.)
It seems like a very Jewish thing to me -- live in the here and now, not to dwell on an afterlife which is essentially nameless and directionless (thinks of a girl in class today asking about the eternal soul/everlasting life; think: Christian concept). But the essential call to fulfill the commandments because that's all there is to do and G-d has already decided the fate of man, no matter his persuasion, seems a little ... frustrating.
Anyone who has done research/work/study whether religiously or academically on Qohelet, please feel free to let me know if you agree or disagree. But from just a few readings of the work, as well as a bit of reading by Michael V. Fox on his analysis of various theories, this is what I've gathered is the gist of Qohelet (contrary to popular theories that it is a gloom-and-doom expose on the tragedy of life and the welcoming of death).