I've got two books to give away. Cocoa Touch fir iPhone OS3 and Beginning iPhone 3 Development.
Wiley::Cocoa Touch for iPhone OS 3
APRESS.COM : Beginning iPhone 3 Development: Exploring the iPhone SDK : 9781430224594
I know, they are not for the iOS4, but they are just a few month old. And to start with, I am sure they will be good enough.
PM if you need them. You could pick them up at the ifc or in Tsing Yi near the MTR.