I think for younger, newer readers, this type of repetition is best. Children learn to read and comprehend words, with the aid of pictures. In my experience with children, they like to make up their own story just by looking at an interesting picture. This book would be great for spending time on each page, letting the children read the simple sentence and then allowing them to use their imagination to create several mini-stories.
"Everything is nothing, with a twist." -Kurt Vonnegut
I think this book works. I have a young relative in preschool. It really bothers her that she cannot read yet, so I think that simple and repetitive sentences are a big help. This method can build confidence through that repetition, and confidence is important when building foundations!
I do not believe repetitive sentences help. Kids can get bored easily reading the same stuff over and over. Maybe younger kids who do not care for the plot would not see it, but older kids will definitely be put off.