This article explains that using repetitive books to help with apraxia of speech is beneficial. My two favorite repetitive books are Goodnight Moon & Brown Bear, Brown Bear. Although I am not a speech pathologist, I work with many children with dyspraxia of the body and apraxia of speech. I definately think repetition and predictability help these children to gain new skills.
My daughter loved her "Goodnight Moon" book so much, that we wore two of them out, and I had to buy a third. Through repetition of reading it to her, and her looking at the pages often, she pointed out to me that the mouse is in a different location on each page. Pretty good of her to have noticed that at the age of 2 years. But I'm sure that if I had not read that book over and over to her, she probably wouldn't have noticed it!