Is John 1:2 just a summary of verse one? John writes in a very simple style. He doesn't write two words when one will do. So, what is he trying to tell us with verse two? He is telling us that Jesus is that one who was with God in the beginning. Our teachers and preachers don't talk much about it, but there are some odd things about the words that refer to God in the Old Testament.
There are several words translated as God in the Old Testament. One is Eloah. It simply means God singular. It is used mainly in Job and some of the Psalms, but it isn't very common. In Hebrew if you want to make a word masculine plural you add "im" to the end of it, so if you add that to the end of Eloah you get Elohim. Elohim is the most commonly used word to refer to God. It is used from Gen 1:1 to the end of the Old Testament, but the odd thing is that it is plural. The most common explanation for this is that it is the plural of majesty. Normally, all the verbs and pronouns used with it are singular, but not always. Look at Gen 1:26 "Let us make man in our image, in our likeness..." and Gen 3:22 "The man has now become like one of us...." Also, Ecc 12.1 "Remember your Creator" should be "Remember your Creators." Our translators are so sure it is a mistake that they translate the plural "creators" as singular "creator." John wants us to think about the fact that someone was with God in the beginning. That someone was equal with him and was called God. Jesus was the one who was with God in the beginning.