Harem, gender reversal, and gender ratio are wish fulfillment stories, so they can be as deep or as shallow as the author chooses to make them. Unlike Danjo-hi 1:5, Gyakuten Isekai is quite shallow, but since its point is fan service and boobies, it should be judged on its aspirations, not its competition. Guild receptionist Ryou works hard at his job, and his professionalism is such that when an S-rank party shows up at his doorstep, he just does his job. Which isn't to say he's perfect - when appraising some items, he accidentally end up dropping a bottle and breaking it. Said bottle contained thefairy Oriondel, who in reward for her freedom, swaps this version of Ryou with the one in another world, one where the values of beauty are also swapped, and men are a mere 20% of the population. So Ryou with his love of beautiful women now has the chance to grab as many beautiful women as he wants in this new world... while his counterpart in the other world can do the same for every hideous uggo he sees.

It's a smut manga, so fortunately the quality of the art is good. The main characters are all beauties, which means when we get to the smut, it's all quite beautiful and erotic. Censored, obviously, this isn't full blown hentai, but it very much is porn with plot. Not that the plot is particularly deep, mind you. It becomes slightly deeper after the main harem is bagged, I supposed, but that's not very deep.

Is it worth reading? It's funny and it's smut, so if that's what you're in the mood for, go for it. Unless you're trying to learn how to do smut, you're not going to learn very many new tricks, but you'll be entertained, mostly in the lower head.