LawnChair is the best option I’ve tried that has a similar design to Nova.
I’ve tried at least a couple dozen launchers since Nova got bought. Most of them are either half-baked or have a very different design (e.g. based on radial menus or text-only lists). If you’re into minimalism, there are a lot of good options. If you want a full-featured icon grid that behaves more or less like Nova, LawnChair is it.
I’m running LawnChair 14 Beta now. You can get it off the GitHub. Last I checked, the version on Google Play was very old.