What can we learn from books that we cannot learn from our own life experiences and observations?

People!

Can you build a trustworthy relationship with a 100 different people to get to know their real self? You could, but it would probably take a lifetime and require all your energy resources. But can you read a 100 books, where main characters are entirely exposed to you? I bet you could! And you may not even need a whole hundred, as a book typically features more than one character :)

By reading a good fictional book we are inuitively learning the whole scope of human psychology in character’s behavior. Gaining empathy and understanding towards other human beings. Discover, that there are perspectives and experiences, that differ from our own, and learn to respect them. Fictional characters often become our role models, and inspire to grow into a better version of ourselves. Their experiences can explain our own feelings and make hardships feel easier.

And, as a purely practical bonus, we can learn from character’s mistakes, instead of ours :)

To sum up, reading fiction is an extremely valuable way to understand people (yourself included!) and, as a result, the world in general, because it all comes down to societies.

P.S. Reading non-fiction is a whole other fascinating deal, but I assumed you wanted to hear about benefits of a general fictional book, so here is my take on it :) Hope it was helpful!)