“RTFM”, as they said. Well, for that, the software have to have a manual in a first place. Cockos has always been a small team between 1 and 3 people developers, and they really prefer to focus on coding than writing documentation (which is perfectly understandable).
Fortunately for REAPER community, a dedicated user, Geoffrey Francis, started, on his own, to write a documentation for the software. It is still updated very regularly, and, after 10 years of continuous additions and revisions, is now a 400+ pages long PDF file! You can download it freely right from REAPER website User Guide page, where it is showcased, as it has become the official guide.
400 pages? Fear not! It seems big (it is), but you don’t have to actually “read” it all. Thanks to the nice Table of Content, internals links, or the Find function of your PDF reader, you will be able to read just the sections you are interested by.
But if you want to read it from top to bottom, go for it! You will see lots of screenshots, tables, schema and explication of some REAPER concepts. This kind of information presentation can help understand concepts, differently than watching a video, so it can be a good complement.
It is especially written for people starting from scratch and wanting to have the basics right, so first steps are setting REAPER, then recording will follow, audio editing etc. From the author words:
This document is intended to introduce you to REAPER and to assist you in learning and understanding how to use this software. It is not, nor is it intended to serve as, a 100% comprehensive encyclopedic repository of every detail, every aspect or every application of all of REAPER’s many, many features.Geoffrey Francis, in the User Guide
It is written an english, not sure if the translations attempts, made by other volunteers, are up to date though. It has to be said that writing a full illustrated manual is a really time consuming task, so bravo to the author for having up to this day successfully keeping all this up to date!
If you want to support Geoffrey Francis work, you can consider buying a print format (aka, a real book) of the PDF. He has also written other REAPER books that might interest you, like ReaMix: Breaking the Barriers with REAPER.
Happy reading! 📖