Why Guru in the form of a Book?

In the word Guru, Gu means to remove darkness and Ru means knowledge so it means that The Guru is something that removes darkness and gives knowledge but unfortunately since we humans did not have any other means to reach out to the sangat with this knowledge, we have to put everything into a Book and so we have this 'Sri Guru Granth Sahib' but then the Sikh felt like that is not right where we have to bow to a 'Book' The fact is that actually we are not bowing to any book but to the knowledge contained in the Book. If we understand this then we will be in a better position to know what we are doing when we bow to The Guru Grant Sahib.