If you have heard about Kandinsky, you will know that he is a '20th century great', and has been credited with making the world's first truly abstract paintings. However, his artistic ambition went even further. He wanted to evoke sound through sight and create in painting the equivalent of a symphony that would stimulate not just the eyes but the ears as well, a new visual form of music. Kandinsky is believed to have had synaesthesia, a condition that allows a person to appreciate sounds, colours or words with two or more senses simultaneously. In his case, colours and painted marks triggered particular sounds or musical notes and vice versa.
On the net, you can find various articles, extracts of his writings, etc, which in themselves are fascinating to explore, but this book "KANDINSKY Complete Writings on Art" is the real answer, as it contains everything he wrote about art. Not a book to read through, like a novel, but one to access and refer to, whenever you need to; at least, that is what I have been doing - very happily and successfully!