What to do with old books

I bought a large tin of Thorntons toffee a week ago (Brazil nut, treacle, raisin and plain) and will use it to dispose of books.
Many of us have far more books than we will ever look at again. These tie us to a place. Our homes fill with books but we become less free as a result. In fact there is no shortage of information on the Internet and there is no need to hoard paper in this way.
I am reading all my novels and then giving them away to people on the train. It is surprising how this brightens their day. The toffee box really comes into its own with 'difficult' books because I can keep the book with a notepad and a highlighter pen. Both of these things aid understanding and I can throw the book out when I am finished.
I am reading a book a week and intend to do so for life.