While the book introduces so many of the plot elements familiar to millions, such as extracting dinosaur DNA from insects trapped in amber, to a giant zoo containing dinosaurs, the book itself is not very well written. The dialog is flat and mainly serves as exposition. There are major plot holes. Characters behave in totally irrational and unrealistic ways. There's a silly and absurd deadline in an attempt to drum up suspense. Children are written in such a manner that we have to wonder if the author has spent much time around kids (11-year-old Tim comes across like a graduate student in paleontology to the extent he knows the leading scientists in the field and the authors of paleontology books, and 8-year-old sister Lex behaves as if she was a 2 year old toddler). There are many, many silly plot devices invented purely to try and create action or suspense - for example a door that can only be opened from one side, in order to separate the children from Grant for a momentary encounter with the T-Rex.
However one of the greatest flaws are the behavior of the characters, and how someone can be injured, watch others be killed, and otherwise be severely traumatized beyond belief, and then feel sorry for a dinosaur and want to pet it and take care of it. Or, after all the death and destruction, the main characters decide to go right back into a dinosaur lair for the purposes of scientific knowledge or other such irrational nonsense.
When one steps back and looks at the book from a distance, and considers only the broad brush-strokes of the plot, it is very compelling and is the foundation on which many movies and follow-up books were based. However the actual implementation of the book - the writing and story telling - is pretty poor.