The book "From the Closed World to the Infinite Universe" by Alexandre Koyré is nothing short of a masterpiece. It is a book you will want read and most likely re-read. But take care which edition you buy. Some editions have the original formatting, which is great while others have a new and very poor formatting.
The edition published by Forgotten Books has the new poor formatting (From the Closed World to the Infinite Universe (Forgotten Books)
). It therefore is a tiresome read. Koyré makes extensive use of quotations from original source material and the poor formatting makes it very hard to tell where a quotation begins and where it ends. Also all the original italics have been removed! Thus you cannot tell which words Koyré wanted to emphasize. Furthermore the Forgotten Books edition does not have an index.
The edition you will want to buy is the one published by The Johns Hopkins University (From the Closed World to the Infinite Universe (Hideyo Noguchi Lecture)
). The Johns Hopkins University edition contains the original formatting. It is thus easy to see where quotations begin and end, all original italics are preserved and it has an index.
To sum up: You should buy the The Johns Hopkins University edition. Yet, if that edition cannot be bought neither new nor used, then you should buy the Forgotten Books edition.