I use a silicone cover made by Ringke called Rearth on my SGP5. I also have a Zagg screen protector on the glass. I doubt it would save me from a drop on concrete, but I didn't want a case that added a great deal of size so I could continue to put it in my pocket. The cover fits perfect and covers the power and volume switch with a well fit dimple for easy use. I'm still nervous about a serious drop because it is not extremely thick.
I went to Youtube and found some videos of people that evaluated several types and settled on this one. You might want to do the same. This forum will likely be a lot of help also.
If you decide on the Rearth be sure to get the one that is "Improved". I've read that an early batch was defective and some didn't fit well. I bought mine off Amazon and am delighted with it. Just thick enough to add a little protection.