It can be very normal, or it could be that your flashlight isn't any good. I have a hard time seeing into some of my very dark green/olive eggs, and one of my EE laid very thick shelled eggs.  
 
Make sure you have a very bright LCD flashlight. Try candling a white egg and see what you can see.
 
Having said that, there's some eggs I've just never been able to see through. I just stick them in the bator, and as long as nothing start weeping or smelling funny, I leave it in.
 
 
There is a learning curve, but with a good incubator and good eggs, incubating really can be fun and easy. I promise!