Spoilers of plot and character are the bane of many readers and authors’ existence. Especially frustrating are those spoilers in the packaging of the book. The cover, back cover blurbs, and the book jacket plot summary are noticeable sources of too much information.
I, unfortunately, just found a new source--the acknowledgement page. The first page of text of a mystery I just read was the acknowledgement page. With just a quick glance at the contents, I discovered in the first sentence of the second paragraph a huge thank you for information on carbon monoxide poisoning.
On the third page of the first chapter, a young ghost appeared with cherry red cheeks which is a classic symptom of carbon monoxide poisoning so one of the major mysteries of the novel--what killed the little girl and her family--was not such a mystery.
So, the moral of this story is, if you have control of the publishing of the book, put the acknowledgement page at the end of the book, not the beginning. If you don’t have control, don’t spell out what your informants helped you with, unless you can be very general.