-- Make yourself familiar with the latest developments [0], such that you have something concrete to relate to.
-- If you are ready to dive deeper i recommended the books of David M. Jacobs [1]. Read his three books in order. If you are in a hurry, read only the latest book. Be prepared for a surprise.
-- I also like Dr. Steven Greer [2]. Some argue that he is a bit overconfident, but overall he is excellent.