The first film could certainly benefit from a more faithful screenplay. While Spielberg made a good movie, he was not exactly true to the source. As it stands, about the first 1/3 of the book is represented fairly well by the first half of the movie, and then both diverge considerably. The entire second half of the book was driven by the sighting of the raptors on the boat headed for the mainland, and Grant's race to get back to the visitor center before it reached there. There was absolutely no mention of this in the movie. Also, the T-rex bought it from the tranquilizer as it was trying to get the kids on the other side of the waterfall (it does not show up at the end of the story and save the day)... a scene that was "lifted" for TLW. Finally, Malcom spent the last half of the book mortally wounded lying in the visitor center, with raptors slowly tearing through the building (the race here was to re-establish contact with the mainland to get Malcom help before he died). So, while there may not be enough to justify a six hour film, it was much more than simply condensing the material.
Granted, this is nothing compared to the hack job he did to TLW (never mind the fact that neither Hammond or Malcom lived past the first book). Literally, the only scene that was somewhat accurate to the novel was the T-rex attack on the trailers. Other than that, well...