I would suggest The Little Prince written by Antoine de Saint-Exupery.

Hi Ernesto. This is a great question! Reading is a great way to improve your english vocabulary and grammar outside of a lesson. It's hard to recommend a book, as I don't know what genre of books you like. Do you like a crime drama, science fiction, romance, comedy, mystery? There's a lot to choose from. If you send me a message, I will recommend some books for you. It's important to consider that at B1-B2 level, you should be in a position to read a general adult fiction book, based on your interests. It might not feel easy but you have the basics in place to start reading 'normal' literature, rather than books for learners. This can feel very difficult at the beginning. A lot of the grammar and vocabulary will be new - and it might feel very tiring and overwhelming. But a good dictionary and persistence will help you through that. As you come across new words, look them up and make a note of them. It can be very helpful to get the audio version of the book and play that (at a slower speed) as you read through. Some learners also find it helpful to read a book that they are already familiar with in their own language. I hope this helps. I wish you all the very best as you embark on an exciting lifetime of reading books in English!

Hi Ernesto, I would suggest trying to find readers. These are proper books which have been rewritten to a specific level. Most of the big ESL publishers (cambridge, oxford .... ) have them. https://www.cambridge.org/us/cambridgeenglish/catalog/secondary/cambridge-english-readers/components

I'm reading "Catch me, if you can"