One of my favourite books when I was little was “Hand, Hand, Fingers, Thumb,” and I was lucky enough to read the hardcover before I read the board book. My favourite part of that book was the “Hello, Jack, hello, Jake” part. You can imagine my shock when I read the board book and that part was completely removed.
I also had the board book edition of “Dr. Seuss’s ABC”. In that version, each section begins with “Big [letter], little [letter], what begins with [letter]?” I was amazed when I first read the hardcover, which has a lot more variety. For example, the entry for O is “O is very useful. You use it when you say, Oscar’s only ostrich oiled an orange owl today.” The entry for X also uses words that end with X and therefore use the “ks” sound that is usually associated with X, while the board book uses “X-ray” and “xylophone”.
These are just two examples, but in general the hardcovers are just so much more fun to read.