"Everybody knows" that Columbus discovered the New World in 1492. Rather fewer have heard that an Irish monk named Brendan may have beaten Columbus by a millennium. Fewer yet have heard of Hero of Alexandria and his aeolipile, a primitive steam turbine which never went beyond being a toy and a curiosity. The late James White knew all these things, and wove them together into an alternative history in which Hero's aeolipile caught on and triggered the Industrial Revolution a millennium earlier, in which Brendan crossed the Atlantic in a steamship and founded a trading alliance with the First Nations which set Ireland on the way to becoming the globe-dominating Hibernian Empire, and in which the adventurers who set out for the New World in 1492 did so in a starship. The crew of the starship, with a couple of notable exceptions, are Catholic priests, who have a secret plan to convert the colonists, and turn what is supposed to be a multi-cultural colony into a Hibernian outpost.

James White is probably best known for his "Sector General" stories about a hospital faced with the difficulties of diagnosing and treating a multitude of alien species. His stories usually involve medical work, and this book is no exception, as the protagonist is a "Healer", a male in a profession dominated by women.

The book is a good deal longer than is strictly required by the central plot, as Healer Nolan is also a story teller, and frequently launches into "well-known" tales of history. (All of which, of course, are completely new to the reader.) The result is a mixture of historical fiction and space adventure which I found completely satisfying. The Sector General books are far better known, but this work is well worth seeking out.