Reddit reviews Freeing Keiko: The Journey of a Killer Whale from Free Willy to the Wild

Go read Freeing Keiko, it's not very long. It was published in 2005, 5 years before Tillikum killed Dawn Brancheau and 8 before Blackfish. In order to explain why Keiko was in such bad shape and why he needed so much rehab after first being moved out of Mexico, the author (a journalist) spent a good bit of time researching and detailing just how horrible captivity is on dolphins, and it's pretty much word for word what they detail in Blackfish. This info has been around for quite a while, but people only started paying attention after Tilly killed Dawn.