Yeah, the succession before the events of the series goes Aegon I --> Aenys --> Maegor the Cruel (Aegon's sons) --> Jahaerys I (Aenys's surviving son) --> Viserys I (Jahaerys's grandson). All of them have their stories told in the book before the events of the Dance of the Dragons even begins to be told.

Fire and Blood is basically a biography of the Targaryen dynasty from Aegon the Conqueror up to one of Viserys's grandsons. The next volume (if it ever comes out) is supposed to follow the succeeding generations up to the events of the books.