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.
Keep in mind that with most glass tops — if they are not inset — you’ll see a green tint on the sides. You can order a speciality glass that doesn’t have this tint but it’s more expensive.On the other hand perhaps you want your space to look cozier (and you need some storage). Stash baskets trunks and old suitcases under simple legged coffee tables to ground spaces that are otherwise too open.