I'm not quite sure why I had both of the books on Copernicus by Armitage on my shelves since at first glance they seem to be the same; or, at least, one is a revision of the other. However, on reading them, I found that they are very different. Here, I'm reviewing them together.

The World of Copernicus was the first one that Armitage wrote (around 1950) and it is definitely for the layman, with very little math and lots of history of the area where Copernicus lived. Copernicus was highly educated, the nephew of a Bishop, and himself a Canon of Frauenberg, having studied for some years in Italy both Canon Law and Medicine. The last section of the book follows those who came after Copernicus through the many years it took for his main idea of placing the sun at the center of the solar system to be accepted, with the history being as important as the science. I found the book to be very readable and interesting even though I had just finished the other one.

Copernicus: The Founder of Modern Astronomy is a great deal heavier on the science and the math; in this case, the geometry necessary to work out the details of the planetary system. The biography and history are still there but the science is more to the fore.
Also, in this much later (by decades) book, Armitage adopts a different style and he is definitely envisioning a different audience for this book. That said, I'm glad that I read both of them as each had a great deal of information that the other lacked.