Recommend a book on Q (New Testament source)

I have been reading up on Christianity and the Bible. I want ot learn more about the possible source of Luke and Matthew know as Q. I wanted to read one of John S. Kloppenborg’s books specifically Formation of Q. However, my library does not have any of his books in their system at all and they are too expensive for me to buy right now.

I was considering getting The lost gospel : the book of Q & Christian origin by Mack, Burton L. which my local library does have. but I don’t know if it is any good.

Does anyone have any experience with Mack’s work? Is this a good place to start with Q? I do want something that discusses the stratification of Q.