As for Forest Gump The movie and the book were completely different stories, the character names and the settings (Alabama and USA and Viet Nam) were the same but only a few of the incidents of the book and none of the funny ones, which there were many, made it on to the screen.

The movie, imho stands on its own and is pretty good. But it is not comedic as the book was and has a completely different point of view.

The book is a celebration of the humor of stupidity.

The movie is a fantasy that says that good people triumph because they are lucky no matter how dumb they are.