Where to start learning to program distributed systems?

I am a recent graduate with a CSS degree and never had the opportunity to take a course on distributed systems, but gradually became interested in the topic. I would love to dive into this topic in the first place in the hope of starting my career as a software developer in this field. I took a course in operating systems and know multithreaded programming as well as a rudimentary knowledge of distributed systems concepts, but that's about as close as I got to a subject that isn't at all close.

Does anyone know of a good place to start studying a subject for someone with a CSS degree?

Do I really need a strong background in distributed systems, especially for an entry-level job, or do you think there are companies looking to hire people with strong programming skills but not necessarily strong knowledge of distributed systems?