Older editions of which books were better than the new ones? 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?
 A: Usually a newer edition is something that at least the author and publisher considered an improvement, so any answers are rather subjective. That said,


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*Ian Stewart's Galois Theory, 3rd edition, is sometimes harshly criticized for ruining a great book, by (1) doing everything over the complex numbers first (leading to some long-winded proofs), and (2) being full of typos. The former is a conscious choice of the author, so its merits are debatable, but at any rate it's a substantially different book from the 2nd edition.

*Calculus Made Easy, by Silvanus P. Thompson. This 1910 classic was updated in 1998 by Martin Gardner, but because both the authors are "men of strong individuality", the difference in styles can be somewhat jarring. Also, John Baez complains that:

Alas, the new edition has been puffed up to 336 pages by Martin Gardener. People must want calculus to seem hard.

A: 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.
A: Ian Stewart, Galois theory.
A: This kind of thing is very subjective, but in my opinion the third edition of Computability and Logic by Boolos and Jeffrey is better than the fourth, at least from the point of view of someone interested in the advanced topics (as opposed to a student encountering the material for the first time).  Some of the more interesting advanced topics were cut from the fourth edition.
