The only bad thing I can say about Shinigami ni Sodaterareta Shoujo wa Shikkoku no Ken o Mune ni Idaku is that its pacing comes across as rather rushed. Aside from that it’s an enjoyable, often bloody, power fantasy of the kind you see fairly frequently nowadays (its main defining feature being the cheerfully amoral female protagonist).
On the other hand I can’t really praise much about Tensei Oujo to Tensai Reijou no Mahou Kakumei. It starts off with a pretty heavy-handed reference to MobSeka, and that sets the tone for what follows. Which is to say a sequence of events and character actions with little attachment to cause and effect. Despite that it still ends up kind of fun as a guilty pleasure… right up until the last chapter of the second book, where it does that frequent Anime series thing of suddenly becoming a completely different sort of story out of nowhere.