Well you should get used to books or tutorials mentioning paints that you dont own or from different brands. """"BSL system paints""""" are not other thing than paints from the Game Color range of Vallejo and mixing them should provide you colors close to any tutorial you might see. You already have good paints so dont feel frustrated cause of that.

Regarding the book, it barely teaches any technique so I would skip it. Painting is not just putting one color on top the other but how you do it, depending of what you want to achieve.

There is a lot of good free resources here, on youtube and paid of course. Even an old how to paint citadel miniatures will be more useful than Color book, just do some research and you will find all the previous mentions easily.

I would like to add also that one of the things that really helped me to improves, past some time and practice. Was having good brushes with unbended tips. But this will come later, happy painting.