As is obvious from the title, one of the crucial elements of this book is the concept of condescension. The following is an excerpt in which Oliphint explains what he means by condescension. Oliphint elaborates and elucidates what this term means and how it applies throughout the entirety of the book. But this quote will give you an introduction to the idea.
First, what does it mean for God to condescend to and be with his creation? Certainly the notion of "condescend" or "coming down" is a metaphor.God does not literally move from a higher location to a lower one, given that God is always and everywhere present. The metaphor, however, is intuitive enough that most would see immediately what we generally mean when we affirm that God has condescended. We mean that God freely determined to take on attributes, characteristics, and properties that he did not have, and would not have, without creation. In his taking on these characteristics, we understand as well that whatever characteristics or attributes he takes on, they cannot be of the essence of who he is, nor can they be necessary to his essential identity as God. In other words, given that whatever properties he takes on are a result of his free knowledge and will, he did not have to take them on; he could have chosen not to create or decree anything. Thus, his condescension means that he is adding properties and characteristics, not to his essential being, as the triune God (since that would mean that God was essentially mutable), but surely to himself (more on this later). (110)
As I read through the book, one of the things that came across as plain as day is summed up in this line: "The very fact that God brings something into existence to which he himself is in some way related entails automatically an act of condescension." (110) I have not read any works that refute this claim. But having read Oliphint's book, the concept seems to be built solidly on the Biblical record of God's interaction with humans and the Scriptural witness to his attributes and character. It also explains many difficulties and paradoxes that are evident in God's revelation of himself.
Again, I strongly recommend this book!