A faithful adaptation, though focusing on a different kind of creature. Almost as if they gave the writer the theatrical script for the movie, but when it got to scenes involving the creature, the description was like a group of elementary kids explaining a battle sequence.
"So then this hunter comes out of the forest and becomes the forest, basically and like, he...he becomes the trees! The army men can't see him because he looks like trees, like a transformer for trees and stuff."
The writer sees that in the script and does his very best to put it into an actual coherent story, but instead of making the comparison that the Predator is like a chameleon, he says the Predator can actually bend his cells to become branches and/or creatures. Whereas, in the film, it's just a cloaking device that has him appear as invisible.
The book as a whole was a good read, albeit a bit outdated, with instead of calling most characters by their names, they're known by stereotypical racial slurs.
Other than that, it's worth at least one read, due to the authors ability to really make you feel like you're in the jungle with Arnie. Heat blazing, bugs buzzing, etc.