The full analysis can be found here.
Foucault tried to prevent the reissue of the book, following the success of Folie et déraison: Histoire de la folie à l’âge classique (1961), but was unable to do so. Instead, he revised the text and changed its title.
The usual way of describing the changes is that Foucault lightly revises the Introduction and first half (chapters 1-4) and provides a new second half (chapters 5-6) and Conclusion. But the second part does make use of the original: Foucault revises the introduction to the second part, writes a new fifth chapter, uses about half of the original fifth chapter in his new sixth one, with some new material, and drops the original chapter six. He then writes a new conclusion in place of the original. The English translation is of the 1962 edition, which is the only one still in print in France.
The changes are important in tracking how Foucault’s thought developed between 1954 and 1962. A discussion of each book and what the changes mean will be in The Early Foucault. But the raw material for a comparative analysis is here. I’d welcome any corrections or additions to what I’ve done, and I do hope someone finds it useful.
There are lots of other resources on this site relating to Foucault – bibliographies, audio files, some short translations, some more textual comparisons, etc.