The book is ok as it is just a one sided view... but guru Nanak is to be truly understood. He never propogated his religion as written in the book, he just propogated "the truth". It us who made it a religion. Sikh is not a religious term. A sikh is a person who is always ready to learn. Simple. He, she or they can be of any religion. It is just a word that explains the characteristics of a person always ready to learn.