Have you read the beginners guide? https://documents.blackmagicdesign.com/UserManuals/DaVinci-R...
At 643 pages it's surprisingly short for how many subjects it introduces. Going further you'll of course want to read In the Blink of an Eye.(978-1879505629) and the Color Correction Handbook (978-0133435542).
And the actual Resolve manual is also really really good. https://documents.blackmagicdesign.com/UserManuals/DaVinci_R...