My interest in ET Book was to use it as the body font for a long-term project.
While webfonts were available, they were simply created from the old Mac Type 1 PostScript fonts without merging the expert sets and alternate figures. I took a few hours and redid the conversions, adding some missing characters in the process. The result is regular, semibold, bold, italic, and display italic fonts which are downloadable on GitHub.
While the conversions were a success, the fonts aren’t usable without resorting to some CSS trickery to make them more legible. The small x-height also requires it to be used at a bigger size than what I’d prefer. So, for now, I won’t be using them, but I may choose to tinker with them to add better language coverage for others who may want to use them.