1) Most children in this school are members of the school library. The most diligent pupils help the librarian in her work
2) They have chosen the most interesting books in the libraryn and recommend them to their friends.
3) For over a hundred years Jane Eyre has been amongst the most widely read of English novels.
4) The magazine which you lent me is very interesting.
5) The garden is at the back of the house and the tennis court.
6) He is a/the most popular playwright in his country. Оба варианта допустимы.