I've read the novel - and it was the kind of mindless fun, with tons of plot holes.. but you could picture easily how it would be animated. not to mention that all 'onii-samas' were like a inside joke.

sadly adaptation to anime fucked it up even further - it prolonged the boring parts for no reason, rushed action, and gave lenghtly explanations of everything(usually by tatsuya-jesus) EXCEPT where it was needed.

i had high hopes for adaptation early on:
if they went with action show(they easily could do it), toned tatsuya-jesus powerlevel down(because we clearly seen that he is basically omnipotent) .. and removed Miyuki's role because she brings nothing of merit to "plot".