This was an adorable look at a subject that's been making the rounds lately in roleplaying circles: namely, the controversy over traditionally "evil" races. Both Dungeons & Dragons and Pathfinder have been actively stepping back from painting drow, goblins, and orcs as inherently evil, but rather misunderstood by other races. In Vampire: The Masquerade, the Ravnos are no longer a clan of thieves and charlatans--those are just prejudices held against them by other clans. Hell, The Spire is an entire RPG built around the drow being ousted from their ancestral home, and enslaved by the traditionally "noble" high elves. It's arguable whether these are changes for the better or the worse, and some approaches have certainly been better-realized than others. But I can easily say that the angle of examining these various cultures through their linguistic differences is something that works heavily in Heterogenia Linguistico's favor.
Everything from the language of scents, to synesthesia, to regional dialects and pronunciation differences between races is explored in this volume, and it makes the various fantasy races depicted all feel distinct and fully realized. It does feel a little farfetched that there seems to be no conflict at all amongst the various races Hakaba meets during his travels, but I'm willing to give that a pass so far, in light of the thought and attention to detail put into all these different societies.
Really, aside from that, the only issue I have is that there's not much of a story behind all this world-building. Hakaba's professor gets injured, so he ends up tasked with carrying on the old man's research for awhile. That's...really it. There are some hints of a plot potentially building, with a cave empty of goblins, where goblins are supposed to be, and one brief scene of a shadowy figure running away from Hakaba and disappearing into a crowd, but so far this is just a pretty interesting slice of life series, with nothing really at stake. Even the inevitable misunderstandings, and gaffs due to language barriers get smoothed out with no lasting repercussions. Still, it's enjoyable, and very creative.
And can I take a moment to say how refreshing it is to find a contemporary fantasy series that's just fantasy, and not about some real-world loser getting tossed into a fantasy setting? While there are a few of those series I enjoy, in general the isekai concept has gotten very, very stale.