Patricia B. McConnell, PhD, CAAB recommends reading
Dog Food Logic: The Science of Canine Nutrition. Patricia comments on this book include:
This quote from the book
“Don’t read this book if you want someone to tell you what to feed your dog.”
and
"I looked at the Table of Contents and found (A ha!) Appendix 5—Choosing Smart: A Dog Food Choice Flow Chart."
"The next chapter I bounced to “What’s So Special About a Dog’s Nutritional Needs,” where we are reminded to pay no attention to the word “no fillers!” in advertising. It means nothing."
I've not read it but it may be worth reading.