Knowing what are the 3 official manuals for the 3 most important projects in the core Nix ecosystem (the manuals for Nix, Nixpkgs, and NixOS, respectively) that together make up the core of the official docs will save newbies a lot of trouble.
The piece they don't tell you is that as a NixOS user, you generally want to look for a NixOS module that supports your application first. Only if you don't see one should you then directly/manually install a package into, e.g., environment.systemPackages.
The landing page that ties these reference docs together and also contains a lot more example-centric and tutorial content is nix dot dev, here: https://nix.dev/
Imo nix.dev is a great entrypoint and quickly getting better. In addition to providing a bit of a map to help you navigate the official docs, it includes the best official starting docs on flakes, and links to the highest-quality external tutorial and expository material about Nix.
Make a mental note about the 3 big reference manuals, and bookmark nix.dev, and you have everything you need to learn your way around the official docs.
> the language-y and build-system-y parts of Nix Language-y manual: https://nixos.org/manual/nix/stable/language/index.html
Build system-y stuff manual: https://nixos.org/manual/nixpkgs/stable/
> the NixOS modules
Using the NixOS module system in the sense of leveraging existing modules is the main topic of the NixOS manual: https://nixos.org/manual/nixos/stable/
Details about the module system mostly live in this section of it: https://nixos.org/manual/nixos/stable/#sec-writing-modules
The piece they don't tell you is that as a NixOS user, you generally want to look for a NixOS module that supports your application first. Only if you don't see one should you then directly/manually install a package into, e.g., environment.systemPackages.
In other words, search here first: https://search.nixos.org/options
And search here second: https://search.nixos.org/packages
The landing page that ties these reference docs together and also contains a lot more example-centric and tutorial content is nix dot dev, here: https://nix.dev/
Imo nix.dev is a great entrypoint and quickly getting better. In addition to providing a bit of a map to help you navigate the official docs, it includes the best official starting docs on flakes, and links to the highest-quality external tutorial and expository material about Nix.
Make a mental note about the 3 big reference manuals, and bookmark nix.dev, and you have everything you need to learn your way around the official docs.