My interest in ET Book was to use it as the body font for a long-term project.
Even though 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 at github.com/barrymieny/et-book.
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.