While I don't particularly like Jack (he's too try hard in most of his videos) I have to hand it to him that he's made a legitimate successful transition from studytube to booktube and probably done the best out of his generation of studytubers (eve, jade, ruby, iz etc) in keeping his audience. His audience and subscriber base definitely helped him get into booktube but in comparison to a lot of youtubers who start making videos about education/when they're in uni, he's adapted his content pretty well.