Like seemingly every book in this series, it is a lovely, colourful, stimulating book for very young children. My baby has recently started enjoying playing with textures and sounds and I bought him this book for Christmas (partly due to my own obsession with pirates!).
It has a wider array of textures than some of the animal ones - for example he also has 'That's not my lion' which is mainly fur textures. My son particularly enjoys the 'bumpy eyepatch' made of corrigated card as not only does it feel strange, but it makes an excellent sound when he scratches it!
Also, for sea-faring little girls, it does feature a lady pirate in a nice pink shirt! Would definitely recommend this book.