It is great that your kid at this stage loves to read and can happily spend hours with a book in hand. Most children this age become independent readers and books really intrigue them. Those kids who become fond of books can be seen with a book all the time, in the car, in bed, everywhere. This is that stage where your child needs to start adapting to the right reading habits and postures, which are going to accompany him in the future as well.
What you need to know
However as parents it is your responsibilities to not only give your child the love for books but also make sure that your child is forming the right habits. Early years of our life are the times when we form habits and parents who are careful and aware make sure that their children form only good habits.
Problems with reading while lying down
One habit that you should try to avoid in your child is reading while lying down. This can be really harmful for the eyes of your child as it can cause a lot of strain on the eyes. The lying down position will also block light on the book so your child will be reading in insufficient light which will again damage the eyes. In addition to that when reading in a lying down position, the distance between the book and eyes is less than the recommended distance, which can harm the eyes. This posture is also bad for the neck and back.
If you do not want your child to start using spectacles soon, then suggest sitting up on the bed with pillows propped up to enjoy the book in the bed while taking care of the eyes as well.