The words of Gad the Seer is a work mentioned in 1 Chron. 29:29. A work bearing this name is under study at the Bar-Ilan University in Israel. the language of this one seems more medieval and is probably not the biblical one, at least not parts of it.

Summery

1. (verses 1-63) God's revelation to Gad the Seer. The Seer sees animals, the sun and the moon, and all that happens is interpreted by the voice of God. The lamb is sacrificed on the heavenly altar but not before he praises the Lord. Gad is told to tell David his revelation, and David blesses the Lord and congratulates Gad for the secret that God has told him.
2. (verses 64-92) A second revelation to Gad concerning the Last Days. There is a prophecy of devastation on Edom that 'dwells in the land of Kittim' while quoting their anti-Jewish opinions. There will be a battle between Michael, the High Prince, and Samael, Prince of the World.
3. (verses 93-104) On Passover a Moabite shepherd asks King David to convert him. David does not know what to do, and he asks the Lord. Nathan the prophet answers in the name of God: 'Moabite male, not Moabite female'. The Moabite stays among David's shepherds and his daughter Sefira becomes a concubine to Solomon.
4. (verses 105-120) A story that praises the nature of King David, the wise judge.
5. (verses 121-130) Before a battle between the Philistines and Israel, the Lord speaks to Gad to tell David not to be frightened. That night a fiery vehicle descends from heaven and smites the Philistines.
6. (verses 131-141) God sends Gad to tell David not to boast of his strength. David admits that all of his strength comes from God. God is satisfied with David's answer and for that reason He decides that He will help the House of David forever.
7. (verses 142-177) David counts the children of Israel. This is a recension which combines 2 Sam 24:1-25 with 1 Chr 21:1-30. Both Biblical known texts, together with some 'additions', appear to be integral chapter in the book.
8. (verses 178-198) God reveals himself to David, telling him he should speak to his people. David gathers the people and preaches to them concerning the Lord's names and titles. David urges his people not only to listen to the Torah but to fulfill it as well.
9. (verses 199-226) Hiram, King of Tyre, asks David to send him messengers to teach him Torah. David answers that Hiram ought to fear the Lord and to fulfill the commandments of the children of Noah. A list of God's attributes is given, and the children of Israel are described as sealed with Shaddai. Hiram and his servants believe in Israel's election and praise Israel. God hears Hiram and sends Gad to tell David that Hiram and his people will prepare His house.
10. (verses 227-249) A praise to the Lord. This is Psa 145 with a different superscription than in the Masoretic text and it includes the missing Nun verse (different from any known version).
11. (verses 250-265) A praise to the Lord. This is Psa 144 with a different superscription than in the Masoretic text (and other minor differences).
12. (verses 266-285) Before David dies he urges his people to adhere to God that it will be good for them forever.
13. (verses 286-353) Except for the first four verses that belong to the former chapter (King David is dead and Solomon becomes King), it is a long story where Tamar, King David's daughter, plays the role of a heroine. This is a kind of addition to 2 Sam 13. After Tamar was raped, she ran to Geshur and later on one of the King's servants tried to rape her. Tamar kills her attacker and she comes back to Jerusalem, praised and blessed by King Solomon.
14. (verses 354-375) A revelation. Gad sees the Lord on His throne judging His people on the first day of the year. An angel brings forward three books in which everyone's deeds are written. The Satan wants to prosecute Israel, but he is silenced by one of the angels. The revelation contains all kinds of details and the Seer does not understand all of them. The revelation and the book end with a blessing by the Seer while an angel answers: 'Amen, Amen'.