I could be wrong, but I think that Stymie is a closer match for the body than Rockwell, particularly due to the serif on the middle arm of capital E (and F). I think that Stymie also matches other details as outlined in the comparison page on Identifont (http://www.identifont.com/differences?first=stymie&second=ro...)
I just noticed that Understanding the Apple IIe also got a re-issue from Call-A.P.P.L.E. in 2024 (print edition from Lulu) - https://www.callapple.org/books-3/understanding-the-apple-ii... .