I think reading is very useful and necessary in our life.
Now teens are not very much interested in reading. 
They prefer other kinds of spending their free time.
They like to spend time playing computer games or going to the discos.
But it's not right. Now every man must be an educated person. 
Not all information that we can find in Internet is true.
Reading books educates us, enriches our intellect.
There are books which have been our favourites since childhood.
Throughout the centuries books influenced greatly on  minds and hearts of people.
Books awaken the young people's imagination.
To my mind books should be read only for pleasure.
Now moral values are very important too.
So books mould young persons' characters.
Very often good books bring pleasure and delignt.
We can read one and the same book again and again.
We can't substitute reading by any other activity.
I am sure only reading must one of the most interesting hobbies of all teenages.

Todays teenagers don't read as many books as a teenager even ten or twenty years back used to. Why is it so? Is it because other forms of communication, learning and 
entertainment have taken over the ever popular "book" or is there some other reason? 

I feel that reading is important to teenagers. There are many types of books that can 
be found everywhere, such as fantasy, real-life stories and humour. Reading not only 
broadens our knowledge, it also increases our creativity, which can be useful for 
students when they are writing their essay. Along with that you developer your concentration and attention giving skills. Most of todays "multitasking teenager" is 
talented but he has a very short attention span. This can be a problem in later 
life. Reading gives them much needed practice - practicing to concentrate and think in one direction keeping the mind open and responsive at the same time. 

I think that teenagers do not really read is either because they do not have the
interest or is too busy to use any of their time to read. Also, it may be due to video 
games or Internet. As there are are more video games for teenagers to play, they would usually choose to use their free time to play rather than spend some time reading.

Hence I think that reading is important.

*честно позаимствовала чужие мысли, хотя вариант Nindanil мне нравится больше.