A CLASSIC OF EFL METHODOLOGY
Julian Dakin's classic text was written when there was great interest in programmed learning, an idea which emerged long before the arrival of home computers which could exploit it.
In the most famous section of the book, Dakin demonstrates a series of programmed learning 'frames' which teach 'Novish', an invented language with some similarities to the structure of well known European languages.
These central ideas quickly went out of fashion because no technology was available to exploit them.
Today, the ideas desrve to be revived and re-examined. Dakin's book is a good starting point.