Reference: viewtopic.php?p=164291#p164291

Modern: There are different kinds of modern josekis. Everybody should know basic modern joseki and modern refinements of earlier josekis. These things, once one knows them, look so ordinary that one can overlook their modern nature. Just read joseki books of the recent years, and they have those basic modern josekis or their modern variations. - Another kind of modern josekis is complicated variations for hard core, strong or trick joseki players. It is possible to spend arbitraríly much time on that, but why? Just to wait for the innocent opponent falling into the specific, learnt trap?

Bad way to study joseki: nothing but rote memorisation. It is possible to learn 500 taisha variations. 3 months later you will have forgotten 499 of them, because you don't apply them. Spend another couple of weeks to learn those 499, and another 3 months later you will have forgotten 498. This kind of joseki study is described by the proverb "Study joseki and become 2 stones weaker".

Good way to study joseki: combine learning move sequences, understanding of the moves, sequences, decisions, learn the related go theory (which is pretty much the generally applicable go theory, e.g., embedding in the global positional context while relying on positional judgement), understanding of the go theory and applying the go theory to the move sequences etc.

Advanced good way to study joseki: the good way can enable one to develop good move sequences in the positional context creatively, so that josekis become as what they are advertised: just model sequences.

38 Basic Joseki: yes, it is a bit aged indeed. Its selection of josekis is too small. The book does not discuss theory in general and carefully. The reader needs to know which concepts of theory to apply, and how. As a first joseki book, it was a good, because the only useful English, choice 20 years ago. Nowadays, there are much more powerful books.

A "second joseki book" with the 50-100 most commonly used joseki: Subotai, you are asking for too little. Only josekis is not enough, see the good way to study joseki. You also need go theory and understanding; theory and careful explanation of the moves, decisions, follow-ups etc. enable your understanding. Luckily for you, just now there is such a book with the right amount (72) of josekis: "Easy Learning: Joseki".

gowan's book recommendations: Takao Shinji's 21st Century Dictionary of Basic Joseki fails to fit Subotai's needs because a) it has too many josekis, b) it does not explain go theory in general and so c) makes understanding too hard for somebody still missing much of the theory. (As a dictionary for other players, it seems to be one of the reasonable choices.) Yilun Yang's Whole Board Thinking in Joseki is not excellent, in particular, because a) it concentrates so much on opening positions that the middle game is neglected and for b) and c) see above. (As a problem book for strategic joseki choices, it can be used by other players, but the reader should be aware that a) there are better Asian books and b) most principles of strategic choices are not trained.)

Mike Novack's advice "you have to learn why each move in a joseki sequence is the correct move" is correct, and is part of the good way of studying josekis, see above.