OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
Edward Lear's Nonsense omnibus : with all the original pictures, verses and stories of his Book of nonsense, More nonsense, Nonsense songs, Nonsense stories and Alphabets by Edward Lear. ISBN 0140087761. Published by Penguin in 1986. Publication and catalogue information, links to buy online and reader comments.
