If I hadn't known it was connected to King's book I would say it was an okay movie, but as an adaptation it was abysmal. I don't think this is attributed to Mick Garris, really, but to the script (as you point out). It needed to be at least two more hours. The audience didn't have time to see the meaningful relationship develop between Mike and Mattie or witness pivotal emotional moments in the novel that helped grease the cogs of a semi-complicated plot. Brosnan brought his best to the game but, ultimately, he was miscast. Too old.
Things I liked:
Max Devore character
The cabin had the right look and atmosphere (although considerably much smaller than the book)
The scenes with Sara singing at the fair.
As always, we still have the book. One of his best.