Simple, static cling HD clear screen protectors from Tech Armor - the 3-pack for only a few dollars - on Amazon are great. Actually feels better and smoother than the naked glass in my opinion.
No image distortion whatsoever. Also no orange peel effect (that is for those that use a wet solution to apply, not the static cling- avoid these types). If you install them properly you will not be able to tell it's even on your device. Anyone who winds up with bubbles has not done a proper installation - there are videos online that you can watch for installation. Use tape to remove small particles between the screen protector and the screen and you will have no bubbles whatsoever. Tech Armor also makes a glass version, but I have not tried these as I assume they would be much thicker.
Have been using these for years and they have saved me from scratches on my screens. I am exceptionally careful with my devices, but my first gen iPad obtained a scratch out of nowhere.