Island of the Lizard King was one of the first gamebooks I beat on my first attempt. Looking back, it's not hard to see why. Unlike most other books in the series, you will only need one of two items to defeat the final boss (but finding both helps more) and one of said items is impossible to miss.
The premise made my head spin, with some mad ruler using an island (run by Lizard people) as a prison colony, before realizing that his plan is falling apart as he has way too many criminals in his domain, and that it would be cheaper to put the lawful people on Fire Island. Anyway, he abandons the prison colony, and the lizard people, now out of a job, run the island as a slave colony and start abducting more people for the slave labor.
I liked the setting a lot. Set on a tropical island, with dinosaurs, primitive warriors, as well as all manner of mutant plants and beasts from the Lizard King's experiments, there is much to like here. It's a breath of fresh air and pretty interesting.
There are a couple of difficult enemies, although some can be avoided with luck or the right items. The final boss is tough, but again, the fight can be made easier if you had managed to stumble on the right things.
It's an uncharacteristically easy book in the Fighting Fantasy series, but also a good bit of fun.