Grip is fantastic. There is a section of leather that wraps from the front around to the back so it helps with the grip on the back. It is a very well designed case. It is so slim that you barely notice that it's there but yet gives good protection.
The rear part of this case is mostly leather it is smooth but I would not consider it very slippery. I personally have purchased three different cases and of the three I like this one the best for the cost
If you have the case open, the front cover will wrap around the back so it won't slide. If you have it closed though, it might be an issue if your knees are bent at an angle. But even then, the leather cover attaches in the back which will still provide some good grip. I love this case, easily the best for the money in my opinion.