This is a careful and tested analysis of the cosmos, the way science studies and learns about reality, and the questions that persist.
Heller starts out with a cautionary note on the misuse of scientific theories by theologians. Later, there is a soft yet stinging rebuke of the works of Teilhard de Chardin. Yet these rebukes to theologians are accompanied by wry asides about science, and a sense that science is not immune from the problems of over-generalizing.
This series of connected essays grows stronger in tone and voice as the book continues. Heller asks why this Universe is explainable, and why both mathematics and questions are able to probe to the core of how the Universe works. This analysis forms a subtle rationale for faith, not over-stated.
A reader gets the sense that these essays are carefully drawn, and have been adjusted over the years to reflect the comments of many. As a result, Heller never goes beyond what a scientist might say, unless there is an accompanying philosophy of rationality that would lead him to go beyond. In parsing this question, one begins to see in the limits of both science and theology a sense of the limits of what a human being can understand.
One also begins to see an order in the Universe, whether spiritual or not.
(Finally, there is explicit within this book a physical theory of the Universe and God, that under the Planck constant and within the descriptive world of non-commutative geometry, we find the timeless and spaceless place wherein God exists. Below the Planck constant, in the timelessness of quantum particles, there is no past and future, there is a now. This dovetails strangely with medieval theology. Heller makes no large claims, but he does not resist the imputation that God exists outside of time, in a way that modern physics is finding mathematically acceptable.... This is so over the average reader's head that my explanation here stretches me too far. A reader wonders, is this bunkum or sound science, bunkum or sound theology? His is a careful and seemingly trustworthy voice, but???)