tl;dr: mediocre slice of life that's slightly more upfront about the sister fucking part
Story: Interesting (if self-indulgent) setting, actual development between characters, and visible plot progress between the first and last episodes.
Art: Given it being about an artist, it fits to have some solid illustrations in the show. Animation is nothing to write home about, but it's not terrible either.
Sound: Not much to say. The VAs do their job, the OP is mediocre, and the ED is fun even if there's not much to it.
Character: If I were to compare it to Blend S's cast, I'd say this one has a better main couple while Blend S has the better supporting cast. There's not much to Izumi and Sagiri, but the time spent on their development pays off, unlike that of Maika and Dino. However, the only side character that stands out here is Elf Yamada, who grew on me the longer the show went on.
Enjoyment: There were some good running gags, but the show really suffers from side character subplots that you don't necessarily care about. I think there was another male LN author that joined the cast half way through, but my brain was kinda numb during that part so I can't remember much of it. Naturally, it's why episode 12 worked so well, as they drop all pretenses of being anything other than an ecchi comedy.
Overall: Probably one of those situations where you're better off reading the manga just to get it over with faster. It's not terrible as some claim, but it's far from something that's worth 4 hours of your time.