I totally disagree that there is anything wrong just because a book is non-jewish. It all depends on the book. Predictably here, people jump and insist that yiddishkeit is all about being close-minded and walling ourselves off from all contact with the world, thinking we are the only good people, and everything and everyone else is bad and Hashem is angry at them all, and he will even get angry with us if so much as read someting that they wrote. He is just waiting for an opportunity to throw us into gehenom, and reading Sherlock Holmes is as good an excuse as any. He is smacking his lips and rubbing his hands in glee as he relishes this opportunity to punish people for reading anything other than what’s on the approved chareidi booklists.
So a child should not read Johnny Tremain about the American Revolution, or Red Pony, or a biography of Einstein or Edison or Abraham Lincoln? We are in this world for a purpose and we have a mission to spread kindness and warmth and to accomplish as much as we can and help the less fortunate and to be a light unto the nations. If we have no knowledge of other people and cultures, we will not have any common language to share what yiddishkeit has to offer. A Jewish child may find the most inspiring book he ever read was a biography of Jackie Robinson, the first black baseball player, or the story of Rosa Parks. The biography of Beethoven is heartbreaking as is his music. And a child may even become motivated to be a bigger masmid by reading about Bill Gates who from his elementary school days often spent nights in the computer lab of his school shteiging in computer theory, and the teachers would wake him up in the morning on the floor of the school.
There is nothing wrong with a child reading about this unbelievably great world that the RBSH created, and all that has transpired, as he learns to separate the good from the bad and to strive for the good.
By allowing a child to broaden his mind and develop some anivus, not thinking that everyone else is bad and worthless, it helps him develop better ahavas habriyos which is the foundation of the world and of all midos tovos.
When he is told that everything is treif and stupid, it leads to the kind of personality disorders that cause people to run around on the streets calling their fellow Jews Nazis. It leads to kids going off the derech because they have no motivation to do anything, since the thought of doing nothing but learning, and not even being allowed to get any secular training to make a decent living is so depressing that they begin to despise the religion. Everything is treif and asur, so they can’t develop any goals or hopes for the future or to use their G-d given talents to better the world, whether by means of curing a terrible disease or inventing a new technology (I don’t mean a new Shabbos blech) or developing expertise in classical music or anything else of interest to them. They remain ignorant of the entire world, and appear to the rest of the world as a bunch of simpletons locked into the 17th century. How can one possibly think of going into kiruv when he comes across as a total ignoramus?
There is plenty to gain from being exposed to other cultures. (The gemara says that various tannaim said oheiv ani es hamedayim or oheiv ani es haparsiim–I love this or that nation because they have such and such admirable traits.)
If you want to believe that avodas hashem means one should be close-minded, that is fine. But at least realize that just as much good, if not more, can be accomplished by being open-minded and friendly to all, and acknowledging the accomplishments of others of all types.