Three Gospels?

I've recently been exposed to a teaching that there are three gospels mentioned in the Bible (http://yesforfamilies.com/covenant/book/ - I've not yet finished reading this, so there may be more comment/retraction to come):

1) the gospel preached to Abraham

2) the gospel of the kingdom of God

3) the gospel of Jesus Christ

The idea is that there have been different gospels at different times and with different peoples.

At first that piqued my interest, but as I consider it further, I see that all three of these gospels are really one and the same.

The good news ("gospel") preached to Abraham (Gal 3:8-9) is that God would justify all nations, including non-Jews, by faith.

⁸ Now the Scripture foresaw that God would justify the Gentiles by faith and foretold the good news to Abraham, saying, All the nations will be blessed in you. ⁹ So those who have faith are blessed with Abraham, who had faith.

The good news ("gospel") as summarized by Paul elsewhere (1 Cor 15:1-8) is that Christ died for our sins according to the Scriptures, was buried, raised on the third day according to the Scriptures, and appeared to several hundred people, including the apostles.

¹ Now brothers, I want to clarify for you the gospel I proclaimed to you; you received it and have taken your stand on it. ² You are also saved by it, if you hold to the message I proclaimed to you—unless you believed to no purpose. ³ For I passed on to you as most important what I also received:

that Christ died for our sins according to the Scriptures,

⁴ that He was buried,

that He was raised on the third day according to the Scriptures,

⁵ and that He appeared to Cephas, then to the Twelve.

⁶ Then He appeared to over 500 brothers at one time,

most of whom remain to the present, but some have fallen asleep.

⁷ Then He appeared to James, then to all the apostles.

⁸ Last of all, as to one abnormally born, He also appeared to me.

The "first" gospel is not a different gospel than the "second": it's merely emphasizing the what instead of the how. All nations are justified by faith in and because of the death, burial, resurrection, and appearance of Jesus.

This one gospel is contrasted with the false gospel of Galatians 1 and 2: The true good news is that all nations will be justified by faith (Gal 3:8-9) via the death, burial, resurrection, and appearance of Jesus (1 Cor 15:1-8); the false good news of Gal 1:6-9 was that we are justified by works of the law (Gal 2:15).

The good news ("gospel") which Jesus preached during his three years of ministry was that the time is fulfilled and the kingdom of God has come near (Mark 1:14-15).

¹⁴ After John was arrested, Jesus went to Galilee, preaching the good news of God: ¹⁵ "The time is fulfilled, and the kingdom of God has come near.

Again, this is not a different, third gospel; it's the same, simply worded differently: Justification is in the kingdom of God, established at the cross.

The good news is that the kingship of Jesus has come, established by his death, burial, resurrection, and appearance, and that this process enables God to justify all nations by faith. To separate this one package of good news into three separate packages is to miss that they are all essentially the same thing, just worded differently.

So:

True Good News - the kingdom of God has arrived, established by the death, burial, resurrection, and appearance of Jesus, which provides justification to all nations by faith.

False Good News - we are justified by works of the law

(All references from the Holman Christian Standard Bible)