A great idea that's executed plainly, and one of the rare instances where the original novel suffers drastically by comparison to its film adaption. Perhaps it's the bad after-effects of a translation, or maybe it's the narrator's scientific background, but I found the tone of this novel to be dull in its pedantry. The dialogue is sparse, and some of the situations in the book are a tad unrealistic; for instance, when Ulysse Mérou is imprisoned by a race of intelligent apes, they refuse to differentiate him from the other, primitive humans simply because he speaks a different language. The human 'primates' of Solar aren't even capable of speech, yet Ulysse, who displays tremendously intelligent behaviour, is dismissed for a large portion of the novel. We share Ulysse's frustration, but not in a good way.
I also found the socio-structures of the apes to be vastly underdeveloped; virtually all orang-outangs have the same pseudo-scientific, incredulous outlook. Gorilla's are faceless construction workers, while the chimpanzees are portrayed as more intelligent and progressive than their lesser kin, albeit modestly. Some of the simian characters perpetuate these prejudices themselves, especially the chimpanzees. This is interesting, but the potential remains untapped throughout the entire narrative. In fact, none of Solar's culture is expanded upon enough to generate a clear picture of the world they inhabit, which is a mighty shame.
Planet of The Apes (or Les Planet des Signes, if you will) keeps the allegory curt. For this, it suffers; at only two-hundred pages, it's a short read, and the lack of distinctive characters reeks of an overblown short-story rather than an actual novel - still, it was enough to set the groundwork for a plethora of films, the first of which addresses the blandness and lack of dramatic tension seen in Boulle's original.
Ultimately it's a competent, if minimalist, allegory that successfully examines man's warped need of discovery. The narcissistic assumption that man is master of the cosmos and nature is dashed on its rear end. Boulle's judgements are distinct; humankind experiments on animals (notably apes) and makes 'discoveries', not for the sake of science in itself, but for mankind's own selfish desire to establish identity through forceful expansion.