Dear A.,
I like Leonard Hodgson's book on the Trinity where he explains two different models of oneness. There is the mathematical oneness of a single digit. But atomic oneness requires the threeness of protons, neutrons, and electrons. All living oneness requires an inner constitutive unity, and God is much more living than we are.
I then go on to explain that God is love and you cannot love alone. That means that God was an eternal family eternally held together by love. If we could know a perfect love among three persons (say a family or group of friends) then you would have the highest form of love and oneness we can imagine.
A unitarian model of oneness (as in Islam or the British or New England Unitarians) can never permit us to be be adopted into the loving oneness of God. Islam has a hundred names for God, but love is not one of them. In Muhammad's heaven we are not part of the loving oneness of Allah, but granted the reward of all that we never got to enjoy here.
As opposed to a model of a mathematically one God, our model views love as the origin of all our creativeness. Some think love emerged by chance from energy/matter. I picture energy, matter, life, and humans as being brought into being by love as the eternal reality of our universe. All else will fade away
Bob.