Want to give the baby something to use right away? You basically can't go wrong in the board book section; anything there can be held on a lap and hold up against the baby's little hands, which will get curious and destructive as the months pass. For newborns, I often recommend Ten Little Fingers and Ten Little Toes, a sweet, lilting text that you can't help but read soothingly.
The House in the Night is also a great bedtime book. (Tip: Yes, every child should own Goodnight Moon, but at least one other friend or relative will realize that.)
Don't feel you have to limit yourself to board books, though. You're not just welcoming a new baby; you're welcoming a new child, and if there's a book for older kids that holds fond memories for you, it'll be that much more meaningful. (Tip: If you're the only Bostonian friend or relative, it may be up to you to get Make Way for Ducklings into the child's hands.)
Imagine the parent saying in a few years, "Uncle So-and-So gave you this when you were born, and I think you're ready for it now."
Really, the possibilities are endless.