Apart from being tied with Jane Street's libraries, Real World OCaml is "deeper" in that it also talks about implementation details. This book has a more "introduction to functional programming via OCaml" vibe. Both are good textbooks with different emphases.

The main author Michael Clarkson also started a similar lecture series on Software Foundations using Rocq (Coq)[1]. Not sure if that's still updated though.

[1]: https://github.com/clarksmr/sf-lectures