I read this book in high school and enjoyed and benefited from it, before taking calculus. I am not sure now after over 50 years, but I seem to recall thinking this may have been influenced by (i.e. largely cribbed from) one of the great books on set theory, maybe the one by Hausdorff. (Indeed the amazon link confirms the two books have highly similar topics headings.) I do recall thinking it was a good source for beginners.