A treatise dealing with the theory of abstract sets in English seems to have been a desideratum for decades, since the "Theory of Sets
of Points" by W. H. and G. C. Young (1906) became out of print
and out of date. This book was the first textbook on set theory
in any language, and includes the elements of abstract sets. No
other treatise in English has appeared, except the short and
concise "Lecture Notes" of Littlewood (1925) which demand an
oral supplement, and the textbooks in German *) and French
(Sierpinski) have not been translated. On the other hand, there
are plenty of American and English books on the theory of sets
of points (some of them quoted on p. 239 of the present book),
but they contain only brief introductory chapters on abstract sets.