In lieu of establishing or maintaining free public libraries exclusively for a single county or municipality in the manner provided in this chapter, the library board of any county or municipality free public library may contract, in behalf of the political unit represented by such local library board, to and with the library board of another political unit or governmental agency or instrumentality with respect to the establishment or maintenance of joint library service upon such terms as may be agreed upon by the several contracting parties. Where there is no existing public library, the power thus to contract shall vest in the county commission of the county or the governing body of the municipality. Included in the power conferred is the determination of the basis and personnel of representation of the local political units on the joint library board administering the joint library service established under this section. Such board, when appointed, shall have the powers and duties granted by this chapter to county or municipal library boards. County and municipal library boards or joint library boards shall have the power to cooperate with all state and federal agencies and institutions in furtherance of the purpose of this chapter, and all municipal, county and joint library boards shall from time to time submit such records and reports as may be required by the public library service; provided, that nothing in this section shall be so construed as to infringe upon any municipal charter provisions governing the administration of existing free public libraries.