Chronicles of Prydain by Lloyd Alexander.
They are a very enjoyable series of books written about fifty years ago in a fairly Tolkienesque style.
There were five in all and I also designed a box for the set. I'll see if I can find some more of those images next time I am down in the vaults.
I don't have all the titles to hand, but the first of these is The Black Cauldron which was turned into a movie by Disney.