my personal opinion is that conspiracy theories tend to be the result of minds unfurling themselves as they've been made overactive and rather imaginative by a pronounced feeling of powerlessness in the world, especially in the face of death. as don delillo says in his novel white noise, "all plots tend to move towards death. this is the nature of plots."
i don't necessarily rule out conspiracy theories (for example, it's a documented fact that the bush administration lied about wmd in order to go to war with iraq simply to gain access to their oil reserves; that is, without doubt, conspiratorial). it is not implausible concentration camps are being constructed in america -- it wouldn't be the first time, after all. but the more complex any conspiracy is purported to be -- and any conspiracy that is far-reaching is necessarily complexly organized -- the more sceptical i am, if only because extraordinary claims require extraordinary proof. seeing a fema camp up close would do a lot more to make up my mind than reading about them or watching videos. one thing that goes a long way toward my distaste toward conspiracy theories is the fact that many 'theorists' are anti-semites, racists, homophobes and generally right-wing nuts. (alex jones is counted among these.)
regardless of the truth or falsity of any conspiracy theory, i think it is definitely true that america (and many other countries) are already far too authoritarian.
if you like novels about teeter on the edge between being about conspiracy theories and merely being about paranoid characters, i would recommend thomas pynchon's novels (gravity's rainbow and the crying of lot 49; v. is also good, but not as heavy on the paranoia/conspiracy shit) as well as don delillo's (particularly libra, about the jfk assassination).