Books should be officially declared an invasive species. They have been accumulating in our present home for forty years now, adding to those which had gathered over the previous forty. They tend to group themselves into sub-species; basically by subject or author, but without the pernickety precision of Dewey or the Library of Congress – they have their own priorities. For example, many years ago I inherited some little leather-bound volumes from my grandmother, and Charles Dickens, Alexandre Dumas and Arthur Conan Doyle still share a shelf as old friends. On the bookcase beside my bed is another self-selected settlement: an eclectic collection of books I pick up when I am tired and want to read a chapter or so before falling asleep, including Elizabeth Goudge, Rudyard Kipling and Vladimir Nabokov. I wonder what they talk about among themselves?