For me, el Tumbao (in conjunction with the clave) is the heart of Cuban music. Specially, it is the groove in many forms of Afro-Cuban music. The word "tumbao" references a particular conga drum used in the early days.
The best book for learning Cuban Bass is Carlos Del Puerto's and Silvio Vergara's THE TRUE CUBAN BASS/EL VERDADERO BAJO CUBANO. They meticulously go through the history of Cuban bass, starting with Danzón and moving all the way to the modern Songo and Mozambique. I highly recommend this book to any bass player of any tradition.
Also, a great accompaniment is Frank Malabe's Afro-Cuban Rhythms for Drumset. Again, this book carefully goes through the history and development of this rich music, beginning with its African folkloric traditions, such as Bembe and Abacuá. I think it's very important for bassist to understand and play as much as possible the percussive elements of all music, especially Afro-Cuban/Afro-Caribbean music.
Here is a variety of tumbaos in 2 3 Rumba Clave, mainly centered around Db (dorian & natural) minor: