If you can rent the 2 disc edition, with Roger Eberts commentary, listen to that.. While I don't always like him as a reviewer, he is a top notch film historian and his commentaries are very informative.
This is one of my top 5 favorite films. I first saw it whan I was 8 years old and my young brain and heart was so blown away.... a cinephile was born that day. I find it smartly scripted, acted and directed., if you want more details, well It's not a film I can disect the same way I could a Hitchcock or Kurosawa film, it's just a solid well made cinematic materpiece. Give Ebert a listen, he should be a good guide through the naunces that make Casablnca special.