yFiles as well. In fact, parts of the book have been written by people involved in the early development of yFiles. I'm sure the dead tree variant of that book sits somewhere in a shelf in the office.
I remember yEd from university 2 decades ago so got excited by the idea of yFiles. Until I calculated [1] the license price - for a single developer on a single project it'd be $14000+$4200 maintenance. Wow.
