I'd be interested to see how well a machine translation of something like this turns out. I'm a Japanese translator so I've seen quite a few, shall we say, questionable translations based off of machine translation, but it is getting better. I would offer to help but unfortunately I don't have the time for something like this, although I could potentially help if you had a few questions.
I also own a couple of Japanese books about Macintosh modification and the 2400c that were published in the early 2000s, but I'm not sure where they are at the moment.
Turns out that the copy I got is in nicer condition than I expected. I'd rather not flatten it and crease the spine for a flatbed scan, so I'm looking into an alternative way of scanning it now. (I don't even have a flatbed scanner here anyway.) Will update when I get this done.