I can't add very much to the other ecstatic reviews for this product. The box (at least at Amazon's discounted price) offers tremendous value for money for 100 postcards, and I really can't put a price tag on quite how much happiness they have brought me.
I went through the full set and found cards of all the Puffin books I read as a child, and was absolutely flooded with nostalgia. My favourites are now tacked onto my study wall, and bring me such a glow of joy whenever I see them.
This would make a wonderful small present for yourself or for friends, and certainly no bookworm who grew up in the 1970s should be without it. I've also since bought the adult Penguin postcard box (slightly lacking the huge charm of the Puffin illustrations, but still brilliant fun); I'm now longing for some bright spark at the publishing house to bring out Peter and Jane and Enid Blyton versions.