TITLE: Older editions of which books were better than the new ones?
QUESTION [5 upvotes]: When choosing some mathematics book to study, is it always the case that one should look for the current edition of the book. Are there any examples when the older edition of some book is clearly better than the latest version?

REPLY [5 votes]: Hausdorff's book Mengenlehre in the first edition had an appendix, omitted in subsequent editions,  on the Banach paradox.  (Later made into the Banach-Tarski paradox by Tarski...)  Someone once told me this was the best, most elementary, presentation of it -- I haven't compared different versions of the proof myself.