All you need to know is here
This is a must read for anyone who wants to delve into Greek oracles. The book presents two different oracles: the Greek alphabet and the seven sages. I really enjoyed how the author was able to present historical background while not making it an ultra dogmatic book. He offers different options of consulting the oracles, making it very clear that each reader should test and find their own styles. A great book with a plethora of useful information. Fully recommend it.