How do I get a general overview?

You can get a copy of the ABPI Code of Practice, probably from your company or, free of charge, from PMCPA

However, the Code itself can be a bit difficult to digest so you may find it more useful to start with An Introduction to the ABPI Code of Practice, by Dr Joan Barnard - a short, practical summary of what the Code is, how it operates and what the requirements are.

If you would like more detail, the book 'The Code in Practice' by Dr Joan Barnard is a practical guide to all aspects of the Code.

More details.