R base

Official manuals about R base can be retrieved from

https://cran.r-project.org/manuals.html

Contribution by the community can be retrieved from

https://cran.r-project.org/other-docs.html

The short introduction from Emmanuel Paradis allows a quick start

Longer book allow a deepening. See for example

R from RStudio developers

And if you want more see https://www.rstudio.com/resources/books/