Quality of the stories in this anthology varies. Some fall flat due to too much unexplained, a thing that needs to be delicately balanced in stories like these. Some nice premises are ruined by trying too hard or simply bad writing. Some are wonderful.
As far as the theme goes, don't be misled by the title: while there are stories based on Cthulhu Mythos, the general concept of this anthology, like editor says in the foreword, is the idea of unknown entity (or entities) beyond human understanding lurking within urban setting. Not that it's a bad thing - old spirit remains, but there are new tales and new terrors from outer space to give us nightmares.
I don't want to talk much about stories because giving away things would ruin the experience, but three I liked the best were "Architect Eyes", "Neighbors Upstairs" and "Slou". I'm afraid I can't explain why I liked them because a lot of it has to do with the plot.
If you aren't that nitpicky about writing, give it a try - you won't be disappointed. There are fascinating ideas and mind-blowing plot twists.
I received a copy of this book through Goodreads First Reads.