I want to text my wife's friend to tell her that the book she loaned us sucked.
That seems very rude. Was she supposed to loan you a different book?
No, but if she was doing her job correctly I wouldn't be in this situation
You're allowed to have your own opinion about the book, but you need to be more nicer about that friend's opinion. They must have really loved it to loan it to you, but you're insulting them by telling them it sucked. You're deliberately making them feel bad.
-\_(tsu)_/-
I do not appreciate that shrug emoji you just sent me as it makes you look like you do not care about that person who went out of their way to lend you a book. I hope you just try to be honest with your opinion with the book, but be respectful of the feelings of the person. It's okay to tell her that you did not like it, but you need to tell her in a non-offensive manner.