As someone who likes to be creative with his writing, I think this book by Patterson is an absolute GEM. The way he describes Tsavo from the thorn scrub, the searing heat, hunting down the brutes, problems at the work camp, you truly feel as if you're accompanying him in the wastelands of Deepest Darkest Africa. The level of detail in this novel would make some movie scripts blush. He is an A+ writer and with his extremely descriptive language, I think he would've more than welcome writing for movies.
Speaking of the movie adaptation from 1996, I haven't seen it. But I have seen clips and other people's reviews. While I cannot make full judgement w/o watching the full film, it seems to range from really mediocre to just OK. Micheal Douglas' character Charles Remington was an absolute mood killer. To quote renowned film critic Roger Ebert, "He looks like a hippie at a Grateful Dead concert." I get that you need a character to relate to the mass public but he's just so much of a sore thumb that you'd just be better omitting him. My outlook on this movie isn't all doom and gloom as from what I've seen, the other actors do a decent job and the score by Jerry Goldsmith is a real treat to listen too. Again, I've not seem the movie. I'm just basing this on what little I've seen on the internet.
Going off a tangent for a bit I think they're two reasons this film didn't stick with audiences
1. By the 90's, films about hunting animals, even man eaters, weren't exactly the most appealing thing for mass audiences. Sharks maybe you can get away and dinosaurs definitely, but mammals, especially canids and felines, are generally seen as animals to be held on a higher pedestal. It also didn't help that The Lion King (a film I loved to death as a kid and still admire) was released two years earlier.
2. This was the 90's. While big cats may have scared movie goers in the early days, those days are now gone. Even some P.H.'s will probably put lions below things like aliens blowing s*&t up (Independence Day) and ferocious CGI dinosaurs (Jurassic Park). I'm sorry but if I had to choose between two lions and a goddamned Tyrannosaurus rex , give me the puddy tats any day.
It's really a shame because as I said, the book's written almost like a movie. I think that if you had the right director, producer, cast, etc., you could have a modern masterpiece on your hands. I think I could make a half-decent movie that at least captures the atmosphere of the book.
tl;dr: book=masterpiece, movie=ok, could've been better, and there's potential for a great movie within the book.