Summary: Maybe, at least for some, the right apologetic is not about logic, but emotion and experience.
It would be hard to over emphasize how many people I respect have been fans of this book. It has been reviewed (and I think generally reviewed accurately) in Books and Culture (long), Christianity Today (short), the New York Times, the Telegraph and the Gospel Coalition (critical but appreciative). (Although not everyone likes it.)
The central idea of the book is that given our culture (and Spufford is writing to a secular UK here, not primarily to an Evangelical US) the idea that we should try to prove our Christianity through logic or proof is the wrong move.
As Alan Jacobs says in the opening of his review, apologetics should be more concerned with rhetoric than dialectical tasks, in other words, follow the interest of the listener, not your own desire to be right.
So Spufford is concentrating here on why, for him, Christianity can be an emotionally right choice, even if he can’t prove it scientifically or logically as many of the New Atheists are challenging Christians to do (or vice versa).
Spufford starts with trying to find the shared belief that we all have about this life. That central shared idea is HPtFtU, which stands for the Human Propensity to F*ck things Up (and he abbreviated most of the time.) Christians call this sin, but I think Spufford is right that calling it the HPtFtU feels more accurate. We can debate the reality or transmission method of original sin, but pretty much no one can debate that HPtFtU is real. We all have been a part of it and we all have seen others participate in it.