I've read some great books by Jack Higgins, others that were quite reasonable, but not worth adding to my permanent library. This was the first time I've read one that was frankly poor. So OK, if you just read and never think about how likely it is, you might still like it, but really...
SPOILER ALERT: Our heroes know that the opposition are murderous, Dillon has already been run off the road and shot at, the nastiest one has dropped rotting fish bait over where they were diving in order to attract sharks, and yet they blithely go to the restaurant on the baddie's island, leave the airplane in the dark, alone, and have a nice dinner and discussion with Santiago (the Big Baddie.) Is it a surprise that the plane was sabotaged? When I should have been on the edge of my seat wondering whether they'd survive the plunge toward the ocean, I wandered off to do the ironing! It seemed to me they deserved to die.
What else? Only a few people knew what they'd found, yet the baddie knew straight away. They didn't even bother speculating who'd told him or trying to do anything about it! Just kept feeding information straight to the traitor.
And then, which I thought quite criminal, they left the innocent girl unwarned, even when by that stage, there had already been a successful murder or two, and she'd already been attacked. It is no thanks to these idiot 'heroes' that she survived the inevitable encounter, though badly injured and having been tortured. They didn't even apologise to her. They were almost as responsible for the attack on her as the Baddies, it seems to me.
I know that arrant stupidity is often accepted in light romances, but asking the reader to tolerate it in what should have been a first-class thriller is asking too much. I'm going back to reading more Indie writers. Technically, their writing may not be so good sometimes, but at least one can be reasonably sure that they're trying.
I do not think that Jack Higgins was trying.