What does it mean by "heart is set on the top of it"?
Native speaker’s answer
Rebecca
When one says that their "heart is set on X," it means that they want to obtain something very much. This can apply to both things and people. The speaker here is expressing that the bear wanted the book very badly. "Top of it" is not typically used with this expression, it may be a mistake on the speaker's part. Ex: His heart was set on winning gold at the race. Ex: Her heart was set on buying the piano, even though it was incredibly expensive.