@washu books are rubbish, i know what you mean. they are all on beginner things. And the advanced ones are, as my wife puts it, wishy washy. its because most people interpret watercolour as gesture driven art, but you can create incredible stuff.
have a look at (google search term) 'watercolour rodney matthews fantasy artist'
who has been a hero of mine for decades. he's UK. there you will see how he works in inks, acrylics, but also watercolours.
now I'll get into trouble here, but I slightly disagree with the amazing @Lee-White (sorry pal!). The reason I wouldn't start with live is that although this is crucial to developing your art, I'd break it down. So working from life requires getting the lighting right, drawing right, not moving your head too much - which reflective surfaces and subsurface scattering and so on can be changed dramatically when you move your head slightly and the light movement changes over the surface. So that's why I say hit a printed off picture first. Copy it. (master copy time). because then you can see how you can get similar effects.
then as soon as you can, paint from life.
the other things is there is a feeling you get to watercolour because of the nature of the medium. one thing I get really frustrated with is when people are trying to paint or draw so that something looks like a photograph. to get everything perfect. If you want a photo, then take a photo. Art has changed from needing to be the portraits hanging in galleries where that was the only visible record of a person. Now we can leave that to cameras (and phones).
interpretation can be best seen I recon when I draw or paint chrome. There is always a bit of the environment involved, but mostly I follow the advice i was given years ago, and it works like a charm,. As long as the chrome is not the main bit of a picture... paint what a desert would be reflected like. Roughly its a white stripe, a blue stripe, a white stripe, a wiggly black edge, dark brown, light brown stripe, and back to white. does it reflect the environment? no (maybe a tiny bit of it to colour if needed). When people look at it do they see chrome? Every time. They only notice its wrong when i tell them.
So don't worry about getting everything perfect. Have fun.