 
<translate> Don amsa tambayar da ke sama, jumlar da ta dace ita ce: An saita shi a farkon shekarun 1990, littafin ya bi Charlie, wani matashi mai son shiga, ta hanyar shekararsa ta farko a makarantar sakandare a wani yanki na Pittsburgh. Don haka, amsar karshe ita ce farkon shekarun 1990. <eng> To answer the above question, the relevant sentence is: Set in the early 1990s, the novel follows Charlie, an introverted teenager, through his freshman year of high school in a Pittsburgh suburb.
So, the final answer is the early 1990s. 