This Christmas, Observer readers can make a difference to the lives of millions of people by doing a very simple thing - helping them buy a book. David Smith opens our appeal Eager children scramble for them in Zimbabwe. Camels carry them through remotest Kenya. They are impossible to to buy from a legitimate seller in Sierra Leone. They have solved problems, launched businesses and careers, created dreams, fired imaginations, changed lives and saved lives. They are taken for granted in Britain, but 113 million children worldwide do not have access to them.