Coffee tables should be the same height as the surrounding seating with 18 inches being a good average (although it will depend on your furniture). If you select a coffee table with a lip make sure the lip isn’t higher than the adjacent seating or you’ll end up hitting your drink against the lip when you try to set it down. The idea is to put your drink down not up.
A coffee table does a lot of work. It needs to hold books magazines drinks food — even games on game night. You might want to put your feet up on it or the kids might need a place for coloring. Plus it’s usually smack dab in the middle of the room where you cannot miss it — so make sure it’s a good one for small glass coffee tables.