in 40 years and more, the number of pages has remained at 104, so i doubt even one word has changed.
in my opinion also, in general for all math books, the earlier the edition, the better the book.
the author puts the most effort into the first edition and it contains exactly his/her vision of the subject as it should be. later ones often incorporate accomodations to the publisher or the fashions of the times.
even excellent revisions such as courant and john, made to incorporate more "rigor" and modern point set topology, have proved softer and less intuitive and less popular than courant's original masterpiece.
updates of van der waerdens great "modren algebra", which omit "elimination" theory", or old concrete arguments in favor of mroe abstract ones, are less useful for exactly that reason, as they become more similar to other books, and no longer sources for powerful but old fashioned arguments and methods.
in an introductory book to a subject that began with Cantor 100 years ago, there is no significant need for updated content.
I read halmos' book just after high school in about 1960, and have essentially never needed any other source for the same basic material.
As I recall, it is sort of an alphabet and grammar for reading modern math books.
