I made two mistakes when deciding to read this series. The first was forgetting about all the people who said the Anime version made significant changes to the source material, while the second was accidentally buying the 5th book before the 4th.
That fourth book picks up shortly after the students leave the deserted island, includes the two brief Ayanokoji/Sakura and Ayanokoji/Kushida interactions shown in the last episode of the Anime, and features a test where the various classes are split into cross-class groups and have to decide whether to work together or betray one another. In terms of event setup and development the Anime is pretty similar… the difference instead is entirely contained to the protagonist; neither his personality nor goals match up.
The Anime protagonist and the LN protagonist are effectively two different people (as divergent as Akagi and Ainz), which completely changes how otherwise similar event developments come across. To put it bluntly: The LN protagonist is utter trash. And since the best part of the Anime was the protagonist….
The 5th book, which I never would have bought had I already read the 4th, is slightly better thanks to Ayanokoji acting a bit more like his Anime counterpart. Unfortunately, the event development is completely centered on a school sports festival. A standard, no twists, generic school life series sports festival (populated by characters with garbage personalities). It’s incredibly aggravating.
So yeah, I can’t really recommend these books to anyone. If you want to check them out anyway though, I’d suggest starting with the 1st book in the series even if you’ve already seen the Anime. The protagonist is so different they may as well be alternative versions of one another.