I had one some time ago which i gave to a friend.... now want to really get into it, any must have?

Thanks!

There is the C# Yellow Book, it's free and lots of people recommend it. I read it and found it very interesting.

I'm the author of this book, wrote it specifically for beginners

http://www.amazon.com/Learning-C-Programming-Unity-3D/dp/1466586524/

Always good to have a few good books on the subject, you may also like to take a look at:

• online C# tutorial (if you can handle the ads), and another.
• CodeCompile's General Programming channel on YouTube (there's another channel there about using Unity3D too if of interest)
• lots of others..

Once you know enough to ask the right questions you will find a lot of what you want to know using your favourite search engine.