This is one of my favorite touch and feel books for babies and toddlers. It's also one of the only ones I know that has an actual page-turning plot (which can be summed up as- the duck doesn't want to be tickled, but you're going to tickle him anyway). It's a great excuse for you to tickle your baby (or for them to tickle you)... but it's also wonderful to see a book in this genre that is more than "Feel the fuzzy bunnies."
My only word of caution is that it isn't a board book (the pages are made out of durable paper) so it might get destroyed by babies. I think it's good for one year olds and up.
Kudos to Ethan Long for creating such a funny and accessible book, for taking this age group seriously and for drawing an utterly irresistible duck. He has a new book featuring the duck called Stop Kissing Me! coming out in August 2007.
Be sure to read Tickle the Duck with a two year old. It's a whole different experience than reading it to yourself.