Indeed. You can still read Eelco Dolstra's thesis [1] from 2006 and the general principles still apply. Some details have changed (e.g. the builder.sh scripts have mostly been abstracted away), but for understanding the Nix store, the Nix language, etc. it's still completely relevant.

[1] Eelco is the creator of Nix: https://nixos.org/~eelco/pubs/phd-thesis.pdf