The core premise of the series -- that the main character believes it's all a joke, while the other characters react seriously to the story -- is a delicately balanced one. You can draw a lot of comedy out of it, but as the plot grew more complicated and the main character started hurting the people he should care about (because everything is make believe and it's all roleplay anyway), it grew unpleasant. His stupidity is funny, then grates bit by bit, then somewhere it becomes cruelty. Younger male readers accustomed to and favorably inclined towards edgy teenage fantasy fare will not mind it one bit, though.
Well at least that's a few dozen manga chapters away at this rate, give or take.