I discovered last night that Appendix B.4 of Fonts & Encodings is almost an exact copy of Appendix B.2, with a couple changes made, but overall the text is not appropriate to the expected content. Appendix B.2 describes the OFM file format, and Appenidx B.4 the OVF format, but in B.4 most of the time it claims to be explaining OFM. Given the size of the tome, I was not too surprised that this is not yet in the reported errata.
Despite everything the book covers I have also managed to find that one thing it does not really explain much about is the special font metrics used by TeX for typesetting mathematics. They are named in the description of the TFM file format, but that seems to be the extent of the coverage. In some sense this is partly okay, because the various TeX documentation explains what the parameters do. The trouble is that I have yet to figure out how you can set them for existing fonts, short of hacking the TFM files generated by otftotfm or afm2tfm manually. You might think this is something you could do with the TeX virtual font mechanism, but Fonts & Encodings specifically says that the metrics in a TFM file must match the virtual font because TeX only reads the TFM.