I'm not certain, why you are investing this insane amount of time in creating these books, but it's surely not to get filthy rich.
1st: about the books themselves. Yes, they are "just" copy and paste jobs, but it's obvious how much work and effort you put into it and the results are truly excellent. You are doing an incredible job.
2nd: While you may not get rich as Musk by selling this stuff for pennies, I'd just like to mention that: I) a lot of people truly value what you are doing. You may not hear that often enough, but it s like that. II) you are doing a incredible job in preserving the memory about these old games for the future. We already lost so much information about historical books, movies and music (not talking about the library of Alexandria). It's a tragedy. YOU aid our(mankind's) effort so that this is not (or only to a lesser degree, thinking of online-only games) going to happen to video games, by condensing and preserving available information in this way.
I'd just like to personally thank you for doing this. Not enough people do that. What you do here is (in a slightly different way) as important to mankind as programming open source software. Thank you.
3rd: I'd like to wish YOU a merry Xmas and happy new year. :-D
Best regards
An admirer of your work.
Personal annotation:
If you don't know where to continue (IF you choose to do so), the PC Engine might be a logical choice. Some alternative suggestions are:
Arcade Games 1980-1984, Sharp X68000, PC-98 or PSP.
If these library sizes are kind of deterring: the PC-FX, 3DO, 5200, Colecovision, Intellivision, Sega 1000 or CD-i have comparatively small libraries.
And then there are of course also those already forgotten systems (at least outside of non-specialist circles) like the Odyssey II, RCA Studio II, Arcadia 2001, Bally Astrocade or the Fairchild Channel F.
If you need some help, I might be able to contribute,