First of all don't worry about cosmology and the big bang and black holes and all that

This piece of advice should be ignored. These are absolutely fascinating topics and you should study them in more depth if you want to. In order to get a popularized taste for it, I recommend beginning with:

-Kip Thorne: Black Holes and Time Warps

and

-Neil deGrasse Tyson, Origins

After you have satisfied your taste by reading more digestable, popular accounts, you can decide if you want to read more detailed and mathematically involved accounts. The downside is that the accessibility of the mathematically rigorous formulations are behind a mass of very detailed and very complicated physics. You basically have to be trained in physics.