The true first edition was hardback published by Alfred Knopf, you have
the first puffin edition. I had a look on bookfinder.com under the title
and using 1961 as a keyword and there are several copies on abebooks for
just over £5
Second (and later) impressions can maintain some value if the first
impression is particulary hard to find to in a collectable condition or
if the cost of a first impression is prohibitive to most collectors.
Also if a later impression has a very goo...
