I am reading this now, doggedly. I do have MA in Contemporary Theology and Ph.D in Sociology of Religion. So I'm not starting from ignorance.
First of all, you have to try and read some incredibly difficult sentences to take it in. In the end, I just plough through and hope.
As I get to understand it, it becomes repetitive! He seems to be saying the same thing over and over again. It is that the human person can only be fulfilled in the communicative community of the Trinity, through the logos of Christ, and anything else is limited.
But it starts to look like a fantasy, highly dependent on the trinitarian construction, whereas it is a mythology. The parallels with Buddhism are mentioned, but Buddhism is more direct and programmatic. So as this repeats, it starts to look like it stands or falls on what the Church Fathers made (rather than the Bible, for example). I sat up when (is it page 114) Williams accused Maurice Wiles of literalism over Adam and sin based on a mistake, whereas this sort of huge claim regarding Christ in the balance sheet is as equal - and Wiles was more sensitive to evolution directly and science that Williams ignores. Williams goes on instead about solidarity, but the solidarity of sinlessness relies on the myth of Christ and all that, as if he did intervene in history in a way Adam apparently did not. In other words, Williams wants it both ways and criticises those who think the Christian myth has encountered a few problems in the last few hundred years.
Buried in Orthodoxy as if (actually) modern thought doesn't exist, despite the use of recent Orttodox theologians, the question has to be asked about the fruits of any of this, from the Philokalia onwards. Do we see the effects of all these traditions? Well, we see Kirill, the head of the Russian Orthodox, thinking that people who kill and bomb in Ukraine can have a shortcut to salvation, and he thinks Putin is the best thing since sliced bread. Yes, there are priests and theologians opposing him, but they are very quiet. Orthodoxy may produce the odd 'saint' but it's not a fantastic record for an institution that takes the cup of power.
This is a book about a huge fantasy creation, a castle in the air. Rowan Williams has some interesting observations online and in some writings, but this is difficult and fantastical and less and less convincing the more he repeats himself. I prefer the critics, the simpler writers or those who try harder to communicate.
Many will be attracted by the title, but like those who bought 'A Brief History of Time' by Stephen Hawking, they won't have a clue what he is on about.
I might try a more detailed essay/ review somewhere. In the meantime, people who disagree might argue on why I get it wrong. Don't argue from doctrine, because the world runs differently - but then I suggest it is all about having it, as I suggest, both ways as if the Trinity works and is credible.