If you want the most reliable and complete version, the best option is to purchase the latest edition. The 3rd edition, updated for the current UNAM curriculum, is the definitive version. You can find it at major retailers:
Historia del Derecho Mexicano Eduardo López Betancourt es una obra académica fundamental que analiza la evolución del sistema jurídico en México, desde la época prehispánica hasta la época contemporánea. If you want the most reliable and complete
Eduardo López Betancourt's Historia del derecho mexicano is a foundational academic text designed to align with the law degree programs in Mexico, particularly at the UNAM Faculty of Law updated for the current UNAM curriculum