My Efner ancestors are not mentioned in any of these books. However, Ezekiel T. Efner was enumerated in Jefferson, Schoharie County, in the 1840 census, and had relocated to Wisconsin before the 1850 census. Thus the last paragraph on p. 43 may be of particular relevance.
Mayham, Albert Champlin. The Anti-Rent War on Blenheim Hill: An Episode of the 40's : a History of the Struggle between Landlord and Tenant Growing Out of the Patroon System in the Eastern Part of New York. Jefferson, N.Y.: F.L. Frazee, 1906.
More about how the rent system came to be:
Brown, John Mathias, 1745-1838. A Brief Sketch of the First Settlement of the County of Schoharie, by the Germans : Being an Answer to a Circular Letter Addressed to the Author by "The Historical and Philosophical Society of the State of New York". Cobleskill, New York: G. W. Bellinger, 1891.
Roscoe, William E. History of Schoharie County, New York, 1713-1882, with Illustrations and Biographical Sketches of Some of Its Prominent Men and Pioneers. Syracuse, New York: D. Mason & Co., 1882.
Sias, Solomon. A Summary of Schoharie County, Giving the Organization, Geography, Geology, History. Prepared at the Request of the County Teachers' Association by Solomon Sias. Middleburgh, New York: Press of P. W. Danforth, 1904.