How do I go about contacting author John Sandford to make a comment on his book, Broken Prey?

Answer 1

write to him in care of his publisher - the address is likely to be found on the first few pages of the book (before the novel, itself), or on the dust jacket, if it's a hardcover.

Answer 2

I would assume you either contact his publisher and/or view his personal website to find contact information.

Answer 3

http://www.johnsandford.org/mb.html

There's a message board at the above site. But take them seriously---you cannot abuse the rules like people do on Yahoo, or you will be barred.