Of note is "Thinking the Way Animals Do", published 1997 and updated in 2015: "A horse trainer once said to me, "Animals don't think, they just make associations." I responded to that by saying, "If making associations is not thinking, then I would have to conclude that I do not think." People with autism and animals both think by making visual associations."
I also find "Animals Are Not Things", which argues for the right to animal welfare based on neurological complexity, very important and thought-provoking.