Reddit mentions of I'm a Big Brother

This is one book we enjoyed and this one was his favorite.

Good luck!

Second all of this. Also pointing out all the fun special things he can do that the baby can't ("only big boys get to eat dessert!" "only big boys get to play with cars!"). If you haven't already, you might read some books with him about being a big brother, like I'm A Big Brother or My New Baby.

Our favorites are the Daniel Tiger book based on a few episodes of the show, I'm a Big Brother, and Waiting

Waiting isn't directly about becoming a big sibling, but it's a good conversation starter.

Our favorite was Joanna Cole's I'm a Big Brother. It will be too young for your 5yo, but probably about right for your 3yo. The language is pretty simple, but it introduces the sorts of things babies do and don't do, and what big brother can do and how to treat the baby.

I read several to my oldest son when I was pregnant with his little brother. He was a bit older than your son (he was 3 by the time his brother was born) This was also about 7 years ago but here are some links.

I'm a Big Brother by Joanna Cole (She has a sister version too) http://www.amazon.com/Im-Big-Brother-Joanna-Cole/dp/0061900656/ref=sr_1_1?ie=UTF8&qid=1331570540&sr=8-1

The Berenstain Bears are always winners. http://www.amazon.com/The-Berenstain-Bears-New-Baby/dp/0394829085/ref=sr_1_17?ie=UTF8&qid=1331570681&sr=8-17

and I loved Peter's Chair by Ezra jack Keats. http://www.amazon.com/Peters-Chair-Picture-Puffins-Keats/dp/0140564411/ref=ntt_at_ep_dpt_2

These might be a little old for your son but if you go to amazon and type "big brother books" you get a whole list.