Yes, it started as a book.
Here's some words about writing the book from the author, Michael Crichton:
Quote:
I wrote a screenplay about cloning a pterodactyl from fossil DNA in 1983, but the story wasn't convincing. I worked on it for several years since, trying to make it more credible. Finally I decided on a theme park setting, and wrote a novel from the point of view of a young boy who was present when the dinosaurs escaped. I then sent the book to the usual people who read my first drafts.
Over the years, I've come to rely on five or six people who read my drafts; generally they have a range of responses. Not this time. They were all in agreement: they hated Jurassic Park.
I got angry reactions such as, "Why would you write a book like this?" But when I asked them to explain exactly why they hated it, they couldn't put their finger on anything in particular. They just hated it, that's all. Hated every bit of it.
I wrote another draft. They hated that one, too. Just as strongly as the one before. Whatever I had done in the latest draft, it hadn't helped.
I wrote another draft, but the result remained the same.
Finally one of the readers said that they were irritated with the story because they wanted it to be from an adult point of view, not a kid point of view. They said, "I want this to be a story for me." Meaning for an adult.
So I rewrote it as an adult story.
And then everybody liked it.
Now, as for differences...
Most of the characters are different:
Dr. Alan Grant - A widowed man, with no romantic relationship with Dr. Sattler at this time (She's actually engaged to someone else). In the book, he also actually likes the kids and makes an effort to talk to Tim when he finds out about Tim's interest in dinosaurs.
Tim and Lex - Take the movie versions and flip them around. Tim is actually the older one that's into computers. He's 11 in the book. Lex is 8, and a typical 8 year old little daddy's girl (she's also very good at getting on people's nerves).
Hammond - He is not the sweet little old man you saw in the movies. He's actually a jerk, caring only about himself, his views and opinions, and money. Despite anything people say to him, or warnings or anything they might give him, he could care less. Even after the park goes down, he is still strongly against harming his animals. In this sense, he thinks he knows more than the experts.
Donald Gennaro - He's not the nerdy, whimpy, loser he was in the movie. He's actually described as being rather muscular, and ends up helping Muldoon in parts of the book. Sure, there are times where he's not terribly brave, but he certainly does his part.
Muldoon - Not too different from the movie, but he's much more cool in the book. He's more assertive and ready for action than he was in the movie.
The only characters that didn't change much were Arnold, Wu, Ellie, and Ian. I mean a few things changed, having more dialog and etc., but not a whole lot that's very noticeable.
Story differences:
It was more than just a handful of people in the island. Almost all of the staff it takes to run the island had been on the island during the problems caused by Nedry. There's at least 20 some people on the island.
The movie added some deaths that weren't in the book, and took away some that were. I think the book and movie only share the death of the same two people. The rest are different. We'll put it this way...
Movie Deaths: About 5 if I'm remembering right.
Book Deaths: About 8 if I'm remembering right.
There's a lot more action in the book, and Grant and the kids end up doing a lot more than you see in the movie, out in the park while trying to survive and get back. There's even some very fun parts with Muldoon.
There's a lot more dinosaurs, and more to the island complexes.
The diloposaurs were actually the proper dimensions. About 10 feet tall vs. that little dog sized creature from the movie, and they had no frill just the red V shaped crest on their heads.
That's all I can get from the top of my head for now.