This book introduces 38 of the most common joseki. It presents some of the major variants of each of them with a fair amount of discussion, much more so than, for example, Ishida's dictionary. The discussion talks about reasons why you might play a certain variant, reasons for certain moves, or what happens next.

I like the book. I'm sure everybody has joseki or variants that they wish were included (I wish that he talked about the magic sword joseki, for example), but you can't put everything into a book like this: if you did that, you'd come up with a joseki dictionary instead of an introduction. The book was written in 1973, which means that it's not as up-to-date as one might want; but here too, if you want the newest joseki and variations, a book like this is simply the wrong place to look.