The "They" would need to be the copyright holders or their agents, and as he wisely doesn't note the particular books he did this with, there is likely no one a

The "They" would need to be the copyright holders or their agents, and as he wisely doesn't note the particular books he did this with, there is likely no one able to take him to civil court. It appears he hasn't done this commercially, so I don't think there would be a case for a criminal prosecution either.