This review may be shorter than the one I normally do but, I will try to give as much info as I can without spoiling the story for you.
The story revolves around Maou a former devil king from another world Ente Isla after a failed campaign of conquest in that world he retreats to Earth where he discovers he doesn't have enough magical power to return, so both he and Alsiel try to live everyday normal human lives as they try to find a way back whilst finding themselves in various predicaments. As you can tell the story doesn't go out of its way to tell something like Highschool DXD does, in fact most of the story just revolves around the funny and ridiculous situations that Maou and his friends get themselves into. The series is more a less Demon/Angels with more slice of life thrown compared to other shows like it. There are many moments where you'll find yourself laughing at what happens, and thankfully the series goes out of its way to put it characters into as many enjoyable funny situation but, rightful ones at that. Many shows out there try to throw to many comedic moments into their shows to the point where they just aren't funny to laugh at, thankfully Hataraku Maou-sama does it right by mixing in a nice blend of comedic value with a serious story to it. On the note of the 'serious' story sometimes it can be lacklustre to see scenes featuring Ente Isla or situations on Earth that revolve around the decisions of the other world however, these scenes far and few between, and most of them are enjoyable to watch because of the comments and actions of the main characters.
The art is good it follows your typical anime art style which holds up well, in the fight scenes the blend magical powers are nice to see but, those scenes are either too short or too few to really bring out the splendour in the art. On the other hand when scenes of Ente Isla are shown that is where the art truly shines, the sceneries may be simple most of the time but, they're brought out by a great mix of colours in the background to make it pop on your scene. And the auras that surround both demon and angels make for a nice hazy but clear design that makes it a bit quirky to look at.
The sound there's not much to say about it really the sound effects for magical powers aren't new they're much the same as most shows that have magical powers. The soundtrack isn't mind blowing to behold but, it's not bad it gives many scenes that nice little touch to make them a bit more lively. The voice acting was good except maybe a few scenes could of had a bit more meaningfulness to them to bring out more scenes more effectively. Where the soundtrack truly scenes is it's opening song which is a great track to listen to.
The characters are enjoyable to watch however, don't expect the show to break any stereotypes here it just does a great job at bringing out the best for its characters. Maou is a likable character for once he's a devil king with intelligence not like some who have no idea or just go with the flow so it makes for a nice change of pace. Emilia is likable too, to be honest I'm not a fan of tsundere's in general as I stated my dislike for one somewhat similar stereotype in Gundam Unicorn however, when it comes to tsundere's in comedies that a direction thing and thankfully Emilia is one that I like. Chiho is another likable character as she's a cute character and makes scenes more lively as she does have that feature about her, she does have somewhat of a tsundere nature towards girls that like Maou but it's a really miniscule level. Suzano I don't know I couldn't really bring myself to like she's not a bad character she just doesn't really bring much to the table for me, she's relatively talkative in a tedious sense most of the time, but that's just personal opinion. Finally Alsiel and Lucifer are basically to me the funniest of the main cast, seeing that in my opinion they have the best scenes (that doesn't mean the other characters aren't funny though). Alsiel adores Maou a lot as his king respecting him with the utmost sometimes it leading to some amusing encounters between him and those that bad mouth Maou. As for Lucifer he did start off as a villain but, he eventually turns into the typical offish laid back teenager of today getting up to mischief over the web. There are a few other characters in my opinion I don't think they're important enough warrant going into detail about.
My enjoyment throughout the show was pretty high I don't remember having any low points whilst watching it just wish there was another season, if so I'd be happy to watch it. On the other hand though it's reached the four year mark when this show stopped airing so they'll be a continuation is debateable.
Overall the show is fun to enjoy and well worth spending a few hours to go through whilst passing some time, don't expect any grand story line like similar shows try to do. As long as you look at it like a slice of life of a devil king you'll be fine. I hope you enjoyed this review and thanks for putting in some time to read it!