This beautiful book about the emotional lives of animals is one of my favourites.
So often in cases of oppression, a line is attempted to be drawn that justifies it. For African American slaves the fact that they couldn't blush (which they could of course) meant they felt no shame and were a lesser species, for South American natives a court case was held to determine whether they were human and therefore worthy of any compassion. With animals, people attempt to deny, despite every external appearance to the contrary, that they feel pain. No evidence is produced to support this, rather it is a philosophical justification to absolve cruelty.
To varying degrees, animals lead emotional lives, rich and varied, and this book gives a mountain of evidence against those still trying to believe it isn't true to justify their contribution to animal suffering.
The other animals are here with us, not for us. You need to read this book, especially if that statement doesn't make sense to you.