I bought Sipser for this very purpose. I found it very difficult without being able to discuss it with anyone to clarify my understanding of the ideas. I would love to work through it, but would need a CS tutor to help me... any takers? ;)

Edit: to be honest it's the maths notation that is a big barrier for me. Until one can read it relatively fluently it's very hard to translate the ideas into a meaningful mental model .