I am currently reading a book by Richard H. Buxton with the aforementioned title. Detailing the manufacture of charcoal (as the author's coke supply was not good enough for his smelting work) and producer gas for running an internal combustion engine, it is very instructive. There are plenty of diagrams and photographs. The retort method for creating charcoal was one that I wished to use for generating producer gas and this book is very detailed in that respect. There are more typing errors than pages but it doesn't affect one's understanding.
It can be purchased by US residents here at Lindsay Books or from here at Camden by European customers.
I recommend Camden for its wide range of books covering alternative technology, steam and stirling engines.