Depends on your definition of practically unknown. With that said, these are the four that immediately spring to mind as being both worth reading and relatively obscure (judging by date of publication in conjunction with being either out of print or with very few star ratings on Amazon). Did Monetary Forces Cause the Great Depression? - Peter Termin, 1975 Termin is still going strong at MIT. His 1975 book was foundational for challenging Friedman on the cause of the Great Depression. Given what was to come in the 1980s this book quickly became overshadowed and destined for obscurity. However, it still provides an appropriate, timely lens to analyze monetary theory without the abstraction that has engrossed economics as of late. The Supreme Court in the American System of Government - Robert Jackson, 1955…
Also recommended in this reply