This is an excellent way to obtain three of Banville's novel at a very reasonable price. The trilogy contains Doctor Copernicus, Kepler, and the Newton Letter. Let me start by saying that Banville made a career transition that is reflected in these novels. Copernicus and Kepler are excellent historic fiction, trying to get into the consciousnesses of these two great men and thinkers. However, the third book, the Newton Letter, marks a transition away from the historic novel to the more sensual, poetic, interpersonal novels of Banville's later career and for which he earned the Booker Prize for the novel, The Sea.
Copernicus covers the rise of the bright young churchman in the Baltic lands that fell between Germany and Poland. The fascinating thing about this novel is the fascinating way Copernicus gradually released his theory of our sun centered planetary system and overthrew the predominant theory that had been held over 2,000 years. Kepler is equally as interesting as Kepler struggles to work with Tycho Brahe and use his data to show the planets moved in eliptical orbits, speeding up as they came closer to the sun. Kepler made this discovery while Catholics and Lutherans fought in the 30 years war and while his mother was tried for witchcraft.
The Newton Letter breaks from this style of historic wriring and is much more sensual, poetic, and contemporary. In many ways the three books don't really fit together except to show the transition of Banville's work away from the historic fictions of great scientists toward more contemporary personal fables of poetic power.