Nothing like starting in at the deep end! I wish you all good fortune with your book
And yes it’s not like getting your paints out! Less mess for one thing!
Although ArtRage has no built-in colour management I would like to say that it can still be used and is used for professional work by many artists as can be seen here: https://www.artrage.com/featured-artists/
Once you are familiar the differences between screen colours, emitted light, and printed colours, reflected light, you do get a feel for what colour palettes aren’t going to translate well into print when working on a screen. But soft proofing is still a vital part of a workflow, as indeed are test prints.
Many print houses doing fin art prints like the two I use are using 12 colour head printers which can offer a greater range of colours, and whilst still not perhaps covering the full RGB range can get closer to it than 4 colour CMYK. So in many ways it can pay to know in advance who is going to print your work before hand and what their requirements will be. It could be that you are safe to work in RGB through out some projects.