Most flexibilities rule engine for .NET [closed]

Question

My upcoming project is relate to sales system, so one of the main requirement is "user can modify promotion by themselves". Promotions is vary, they give me some of them.

1. Buy 1 get 1 free, Buy 2 get 3.
2. One for 30%, two for 50%, three for 80%
3. Buy product A will discount 30% for product B
4. 20% off for more than 20$ per transaction

I know a little of rule engine, please suggest me a book to learn it too.

Answer 1

A previous SO answer might be of help: Looking for simple rules-engine library in .NET

Have you looked at Windows Workflow Foundation