To Be

Spanish has 2 words for "to be"

Which is often confusing to me. 

What's more, I'm studying a lonely planet phrase book, and they use 2 different forms when describing 2 different marital statuses:

I am married: Estoy casado. 

I am single: Soy soltero. 

I guess I should consult someone who can really speak it. 

Is the guide correct or do they need to tweak it?