In literature, the tone is the term that represents the feeling and sensation that the author or poet wishes to convey to the text reader through the words and scenes narrated in the presented plot.
In the poem quoted above, we can see that the author presented the tone of discovery, because he uses words to show how books allow the human being to discover places and feelings that he does not know, allowing the reader to enter a completely new world and ready to be explored and discovered.
Probably one that has many questions (that can be answered), with lots of information, it is a subject that people can easily comprehend and it has many fun areas and components to get people into it