This may have already been mentioned, but if you want to know where the story goes next, the original source material is in the Bible. The Old Testament "First book of Samuel" (or I Samuel). As cool as this show is, the book as in most cases, is better. Just keep in mind, it's translated from ancient Hebrew, so it doesn't exactly read like a modern novel. But it does explain where the "high speech" of the show comes from.
Silas = King Saul
Jack = Jonathan
David Shepherd = David
Michelle = Michal
Rev. Samuels = Samuel the prophet
Chapter 1-3 tell about Samuel's birth, and about God choosing him as his messenger.
Saul (Silas) comes on the scene in ch. 9 and is chosen as king in ch.10.
David is chosen to replace Saul as king in ch. 16, and fights Goliath in 17.
chapters are short, sometimes only a page
The writers of the show did a pretty good job of taking the main plot points and translating them into a modern setting, but the book is pretty different. Michal (Michelle) has a smaller role in the book, and Abner eventually serves under David's command. As politics was pretty ruthless in the ancient middle-east, the book has a lot more violence. It would have been interesting to see if/how the show would have showed some of the events in the book, like when David pretends to be mentally insane to keep from being discovered by Isreal's (Gilboa's) enemies when he is hiding from King Saul.