I don't necessarily begrudge the authors for including chapters on advanced topics, it's not like people have to read the whole book. But you raise a valid poin

I don't necessarily begrudge the authors for including chapters on advanced topics, it's not like people have to read the whole book. But you raise a valid point. For languages like OCaml that are both large and also veer into PL research territory, some guidance about how many of the advanced topics one needs to understand to be a "real world" programmer could be a big help to the language's adoption.