I am a big fan of books to introduce the idea of new concepts for children and we loved "Hello Baby" as we prepared for the birth of DD2. I don't know you book Sunshine but it sounds lovely.

BTW, is there a good book on birth & the new baby? I think DS is ok with the pregnancy idea, but might be nice to talk more bout what's coming next
I found that most books about dealing with a new baby focus on the jealousy issue. Not a bad thing mind you, but if there is no jealousy you need a few different options.

I bought:
"Peter's Chair" - written by the author of "whistle for willie" Ezra Jack Keats (does anyone else remember this gorgeous picture book??) Peter gets a bit jealous when all of his baby furniture is painted pink for the new baby.
"Za Za's Baby brother" - Lovely bright picture book by Lucy Cousins of the Maisy fame. Simple and sweet, good for little ones. Confusion for Za Za about not getting any attention are resolved with cuddles when the baby is asleep. Za Za also realises that his baby brother can be fun to play with. This one came with a DVD animation of the story too. Bonus!
"My new baby" - One of the Jeannette Rowe series. Really simple bright picture book with flaps to lift simply listing things about babies. Good for younger children.
"Too small for honey cake" - Gill Lobel and Sebastien Braun. A little fox gets a little angry/jealous of all of the attention the new baby gets. I liked that this book resolved the jealousy issue and resolved it with a practical mummy still loves you angle. It is a little complex, but it is amazing how much little ones take in. It does help open up discussion if a sibling is getting all those big scary angry emotions and is having trouble processing them. DD1 at 2.5 made no comment when we read it to her but a week later, came up with amazing insight after DH and I had a little argument. I said to DD afterwards, "sorry, honey. I was just really angry with your dad but I do love him and I do love you." She replied matter of factly, "just like the fox in the story."
"I'm a big sister" - One of the Joanna Cole series. This was a wonderfully simple one with no focus on the emotions such as jealousy. This one mentions the "I'm special because I am a big sister" and takes the I can do things the baby can not because I am big angle.

The only issue I have with most of these books is that the images of feeding the baby are usually bottle feeding. This doesn't make much sense to DD as she has only ever seen breast feeding.
I did find a $3.00 book at Dimmys/Forges "My new baby" by Annie Kubler. No words, just images of life with a baby and mum is breastfeeding in two images. Not bad!