Warning - Wikipedia contains spoilers
In The Last Battle, Lewis brings the Chronicles of Narnia to an end. The book deals with the end of time in Narnia and sums up the allegory of the books by linking the experience of the human children in Narnia with their lives in this world.
The book deals with the reign of the last king of Narnia, King Tirian, who must face the fact that strange and uncomfortable things are happening to his land. This represents the ideas of signs of the end of time, as may be found in the book of Revelation in the Bible. The king is joined by two of the children, who help him battle an invasion by an army from the southern land of Calormen. The Battle leads to the ending of time as Aslan steps in to bring time to an end. Those who have been loyal to Aslan or to the morality upheld by Narnians join Aslan in Aslan's land (heaven) while those who have deserted him are carried off to an uncertain future by Tash. It becomes clear that all those who had travelled to Narnia in previous books have been reunited in Aslan's land where they realise that Narnia and our own world are linked and that they have in fact died on earth and can enjoy an afterlife in a perfect version of Narnia where they are reunited with characters from previous books.