by the way you said it, it looks like d4 is a huge blunder
From's Gambit Response?

it is probably a mistake or a book move
You were right the first time, a mistake. Surely not a book move.
Just think about it. What logical sense, if any, does d4 have? None! You give Black ...e4, which no matter what White does can be protected with f5 or d5, and White has trouble developing with that pawn wedge in his face. It is not a reverse Stonewall as ...e5 is not prevented.
Hello
I've stated to begin to look into the Bird's Opening, and one of the common responses is the From's Gambit. What happens in depth after white uncorks...
d4????