Learning through electronic gadgets, has become very common these days and due to which most young kids spend their time on these applications. I agree that books cannot be replaced by these devices however computers or televisions, has also played an important role in the overall evolvement of students.
In order to develop some skills, such as reading and writing one can always rely on the books for an example, reading texts manually from books gives an idea of how to write properly with full concentration, which cannot be possible while studying online or through the electronic gadgets. Hence books have their own vital role when it comes to develops such skills.
On the contrary nowadays due to advanced technology, it has become necessary for every children being up-to-date in order to be successful. Through learning, kids can develop their imagination skills with the reference of videos beside the theory, It becomes very easy to understand even the hardest topics.
All in all, I would say both books and online study is important for the growth of a child