While those links are hugely interesting, I think a more contextual figure drawing book (try Loomis – Figure Drawing), would be more appropriate than de facto anatomy tome. The idea of a beginner improving the figure that way (and specifically from antiquated sources, which could easily be misleading or inaccurate) actually seems a bit mad to me. Gray’s is cool; I have a copy inherited from a nurse, but might only have really used it a couple times for zombie viscera or something.
You might actually be better off focusing on honing your observational drawing skills (measuring, proportions, shapes, fluency) to improve the accuracy of your figures and most else. You can always keep ref. handy 'til it sticks.
By no means am I saying that these are best ones out there (as I said most of them are pretty terrible, especially the older ones. I noted the ones that I saw as the best); but they do represent the muscles and skeleton in a very clear way, to me at least.
Perhaps I've had an unusual way of learning anatomy to others, but I don't see the big deal about learning from those, nothing mad for sure (I swear I'm not crazy
).
In terms of accuracy the ones I noted are pretty accurate in my opinion, nothing really irregular catches the eye; and sure there might be some small muscles that are inaccurate (which is doubtful within itself seeing as all of them are drawn directly from dissected bodies) ,but you aren't expected to remember any those (like in the area between the neck and traps for an instance; looks like a bunch of strings to me, but it has a configuration).
The muscle groups are largely the same as the modern ones would depict them, if not exactly the same (muscle groups likes the pecs, delts, biceps, triceps, etc... big muscles).
About Grey, a rather interesting example you give to its use, but I hope you didn't misunderstand me as I wasn't referring to the organs and stuff, but to the skeleton and muscle illustrations, which might be few, but still are pretty great in my eyes.