The book contained quite a few carved plates. Basically plate XII, was focused on, but other plates were mentioned and there was an out of place quality to all of the pictures.
I'm not sure what you mean here by "an out of place quality". As I recall, the description of the plates illustrating the volume were in general quite neutral, almost nonexistent, focusing on the fact that the book kept opening to this one disturbing plate.
What I am suggesting is that the book was evil.
Again, I'm not sure where you are getting this, at least from the text itself. It may, however, have made that impression on you personally. But the Regnum Congo is simply an account of travels in the region. To quote from Joshi's notes to the tale:
Filippo Pigafetta (1533-1604) wrote a work in Italian entitled Relatione del reame di Congo et delle cironvicine contrade (1591), an account of the travels in the Congo of a sailor, Duarte Lopes. It was translated into Dutch in 1596, into English and German in 1597, and into Latin (by A. C. Reinius) as Regnum Congo in 1598.[...] The plates by the brothers De Bry first appeared in the German edition of 1597.
-- The Call of Cthulhu and Other Weird Tales, p. 372
As I recall, the plates were not included in the Latin edition, though I could be misremembering on this. At any rate, there are several errors in Lovecraft's tale concerning the book, and one of the most important is the emphasis on the cannibal butcher shop, as can be seen from the following reproduction of the actual plate:
http://www.angelfire.com/games5/deltagreen/ForbiddenLibrary/RegnumCongo.html
(And I wouldn't take too seriously any of the information included on that page, as this is material intended for a Lovecraftian game, not factual scholarship. The reproduction of the plate, however, is genuine.)
The point being, that this is a minor part of a book of travels, not the main thrust, making the book anything but evil... though, as I said, it may have well impressed you that way from the tale itself; that is an individual reaction, and quite valid on that ground, but it was not something Lovecraft himself is likely to have intended.
The title of the story is a clue, that the picture was significant.
Yes, the title is significant (all his titles are, in fact), though the meaning here seems to be more the perversion of the aged inhabitant of the house and the secrets being hidden within that house; as well, perhaps, as Lovecraft once again drawing that line to the tendency of people in lawless conditions repeating the actions of primitive, perhaps even pre-human, conditions.
I think that the work that was going on upstairs was not simply butchery, but it was an act influenced and brought on by the picture (a supernatural act in progress). There doesn't appear to be a whole bunch of victims in the vicinity to support continuous murders. It is as if time stood still.
That last is an interesting point, and may apply to what I mentioned earlier. This is an idea which -- though never realized fully or developed as well as it might be -- also plays a part in the events of "Medusa's Coil" (a revision he did for Zealia Bishop) and "The Ghost-Eater" (a revision/collaboration with C. M. Eddy, Jr.). As for it being "an act influenced and brought on by the picture"... I think there is a deal of truth to that, but I'm not sure there is anything actually supernatural at work where this aspect is concerned; rather it fits in with what Lovecraft is saying in the opening paragraphs about how these Puritan people, in isolation, reverted to such actions as mentioned above:
In such houses have dwelt generations of strange people, whose like the world has never seen. Seized with a gloomy and fanatical belief which exiled them from their kind, their ancestors sought the wilderness for freedom. There the scions of a conquering race indeed flourished free from the restrictions of their fellows, but cowered in an appalling slavery to the dismal phantasms of their own minds. Divorced from the enlightenment of civilisation, the strength of these Puritans turned into singular channels; and in their isolation, morbid self-repression, and struggle for life with relentless Nature, there came to them dark furtive traits from the prehistoric depths of their cold Northern heritage. By necessity practical and by philosophy stern, these folk were not beautiful in their sins. Erring as all mortals must, they were forced by their rigid code to seek concealment above all else; so that they came to use less and less taste in what they concealed.
This seems pretty straightforward an explanation for the events, without drawing on the supernatural for his perversion.
As for the comment about "simple butchery" and
The blood that fell down from the ceiling must have been lamb's blood, and than the blood drop would have some form of symbolic significance. I would argue that it was lamb's blood and not a human victim.
I think the text is actually quite clear about how he had become more and more perverted in his taste for "victuals [he] couldn't raise nor buy", along with the strong hints that he himself had done away with Parson Clark and the district schoolmaster (and, as the events of the tale indicate, quite a few others as well over the years), making the likelihood of it being a lamb extremely slender. And if it were a lamb, why would he be butchering such upstairs, and acting so furtively about it, when there was nothing abnormal about such butchery by a yeoman farmer to begin with? No, this is, I think, one of those cases of Lovecraft being a tad too explicit perhaps in driving home his point about the culinary habits of the strange old man of the tale, and the inference that it is yet another person he has killed and is preparing for his table seems pretty inescapable.
As for the scarcity of such victims... well that is an interesting point; but one must remember that even such isolated roads as the one which led by this place were still the only ways to get to some regions at the time; what we know as modern freeways and the like still being some decades in the future. More often than not, such lonely backroads were traveled by itinerant salesmen, preachers, antiquarians, and various other types of travelers seeking out the smaller towns and villages, and these were not infrequently on foot (automobiles being still a rare commodity and bicycles being only slightly more common with such travelers). So he would quite likely have been able to "keep his hand in" at least periodically; though the coincidence of such having happened on the same day as the narrator's visit
may be considered a stretch.
There is talk of the Almighty as well as a Bible, but the storm did slowly build in intensity so it is ambiguous as to what caused the thunder bolt.
Yes, there is such talk, but again, this is part of the man's Puritan background, where "theological self-examination" was involved with every aspect of life; that's the nature of a theocracy: nothing is entirely secular; it is all, even the most minute particular of a person's life or thought, involved in the Divine Plan in one way or another. Again, though, this does not indicate anything in the tale to support the idea that such a Deity even exists, let alone takes such an active role as to send a thunderbolt at the opportune moment. As for the storm building slowly... storms quite often do, of course, and I'm not sure where that would indicate such involvement, either. All told, I think this is imposing a reading on the text, one which it does not itself support, rather than discovering such a reading in the material itself.
Well, what gets me when I read Lovecraft is that there is always talk of "brothers" in these stories and here is another example involving the brothers De Bry.
Anyway, the picture is the focus and it was perhaps not fully explained, but every time this brother talk enters these stories, not far behind is witchcraft and monsters/aliens.
I think your point about brothers is an interesting idea... it ties in with the idea of Lovecraft's use of "doubling", which is indeed a common motif in many of his tales. I'd like to hear more of your thoughts on this aspect....
Last of all points, this version of the book was written in Latin. It was a book that was supposed to talk about the Congo region of Africa. It sounded like there were oddities/errors within the book, things out of place or trapped or drawn wrong, etc.
Well, as noted earlier, it was simply a book of an account of travels, and such were frequently riddled with such errors, even when not written down second-hand (as this was). This sort of error dates back to Pliny at least, and makes for some peculiar looks at the world outside the writer's usual sphere....
At any rate, an interesting discussion. Keep your thoughts coming. While I may or may not agree with them, it's fascinating to see what someone else makes of these things....