I liked Crichton's writing. It's a healthy mix of the over-detailed writing of Tom Clancy and writing of John Grisham with is often a little too pedestrian. Crichton did a great job of weave some fairly complex science and math into his story, giving the event an air of plausibility.
Like Grisham, Crichton sometimes appeared to be "writing to the movie." Take this passage, where Dr. Grant is riding down a river on a raft with two kids:
Grant heard sudden shrieks from the trees above, as the microceratopsians scattered in alarm, shaking the branches. The big head of the tyrannosaur lunged through the foliage from the left, the jaws snapping at the raft. Lex howled in terror, and Grant paddled away toward the opposite bank, but the river here was only ten feet wide. The tyrannosaur was caught in the heavy growth; it butted and twisted its head, and roared. Then it pulled its head back.This might be more aptly described as "writing to the amusement park ride."
However, there were times when Crichton's prose rose above the level of pithy action novel and made me take notice. The best example of this was Dr. Ian Malcolm's (played by Jeff Goldblum in the movie) two-page rant about science as an outmoded belief system that was destroying itself.
The most striking difference between the book and the movie was the character of John Hammond, the man behind Jurassic Park. In the movie, Hammond was an avuncular character, an old man with enough money and influence to make his pie-in-the-sky ideas come to life. You did not judge him to harshly at the close of the film. His was a much different character in the book. He was conniving and driven by profit, and more than any other character, you hold him culpable for the disastrous event that take place on the island.
Jurassic Park was a fun, quick read. I liked it enough that I'll read The Lost World.