At this point, White Fox as a studio is a (fairly) safe bet when it comes to watchable anime series. Naturally, there is a variance in quality from 'alright' (the Devil is a Part-Timer) to 'legitimately excellent' (Steins;Gate), and I'm sure they've put out some stinkers too, but one goes into Grimoire of Zero expecting a certain degree of quality. Fortunately, expectations are met. Sadly, 'watchable' is the best that can be said.
Grimoire of Zero follows Mercenary, a mercenary (it isn't his real name) who has been afflicted with bestial qualities. This is a world in which 'sorcery' and 'magic' are intertwined but distinct concepts, and in which witches are feared by the general populace and burned at the stake. Mercenary hates witches himself, but finds himself partnering with Zero, a young and pretty magic user, after another witch tries to kill him and take his head for use in rituals. Zero wants to find a magic book which has been stolen; Mercenary is promised a human (as opposed to beastleaven) life. It checks out.
Part of GoZ's early charm is in its simplicity. I've seen this series compared with 'Shrek' and, though they're not completely analogous, there is some correlation. Mercenary and Zero have a reasonably enticing, and thankfully mostly platonic, relationship which often centres around good-natured teasing and the kind of slow, warm growth of closeness that we've come to expect from these kinds of things. It gets a little bit repetitive at times, however, so conversations about fur and sleeping thereon are sometimes broken up by Albus, the aforementioned 'other witch' who is basically the 'adrogynous blonde angsty young teen character' that somehow amounts to an anime trope (Yukine from Noragami is another example). Albus isn't particularly interesting and sometimes proves mildly irritating, but is a worthwhile addition if only to keep Merc and Zero's dialogue from getting staler than it already threatens to be.
The rest of the cast balances on a similar wire between mild interest and tedium. Save for another beastleaven character (who seems to be pushed as likeable in later episodes despite being introduced as a literal slave owner) we have a respected but deceased witch whose legacy, her unwarranted execution, weighs heavily over proceedings, and Thirteen, the villain of the piece. Thirteen is actually one of the more interesting villains this side of Re:Zero's release; his motivations and dastardly plans are intricate while arguably following a certain twisted logic, and raise him above the set of morons and play-doh people which 2017 has foisted on us as antagonists so far. The plot doesn't especially call for a platoon of deep and difficult characters, so we don't get that many, which I don't especially have a problem with. On the other hand, it is also a plot which begins to trundle a little into the territory of the commonplace as we near the finale, which is a weird thing to say about a series concerned with magic books and tiger people.
One of the major themes in GoZ is that of the accessibility of magic and its pros and cons. The show is surprisingly nuanced in how it addresses the problem (as opposed to The Irregular at Magic High School, aka. 'equality is bad and you should feel bad'), often playing with the idea that magic for the masses is a beneficial concept but that foolish and unstaggered access could be damaging. Things like this can sometimes buoy up a series which, though not horrible to listen to or look at, doesn't have the most dynamic action or the most engaging conversations in all of animedom. There's also a lot of typically White Fox-esque humour, purposeful anti-climax and accusations of perversion, which might put some people off. GoZ gets a lot of mileage out of gags about sex slaves and sniffing used clothing, which is a sentence I never want to have to write again and which isn't particularly endearing. Other themes are similarly awkward in their execution; the revelation that beastleaven sometimes eat humans in feral rampages isn't especially necessary, given all of the other reasons we're given as to why humans mistrust them, and the series can sometimes feel a little too 'neat' in how it wraps up threads. The ending, for example, seems a little too 'nice' considering the circumstances, although its still hardly the worst closure that anime has tried to feed us; I for one still remember No6, and Cowboy Bebop, and True Tears, and Darker than Black, and Darker than Black Season 2, and so on so forth.
TL;DR... All this in mind, GoZ is, as I say, perfectly watchable. On the other hand, it pains me a little that this is the second-best anime series of 2017 that I have watched thus far (after Scum's Wish). It's a bit like saying that the second-best superhero movie that you've seen is Thor 2; not exactly the end of the world, but...