It was a maths (pre-concept) book by Blueberry publications. And a text book by Frank Bros Publications. I also worked as a Kindergarten teacher for 5 odd years . And hence created innumerable in house story illustrations too :) . And then I moved into fine arts and started working on my collection and got into Aqua training ( family business ) .
I agree that there is a huge market demand for digital illustrations.
It is more vibrant , cleaner. Also faster and easier.
A base of traditional art knowledge and digital medium is a great qualification in the field of illustrations :)
Perhaps I will give it a try, as you suggest, @airmatti :)