New Delhi, Oct 11: Just when Amitabh Bachchan was making a foothold in Bollywood, Rajesh Khanna, already a superstar, had sneered at the angry young man's punctuality, calling it a clerical trait, a new book has revealed.While Khanna was known for throwing tantrums and coming late for shoots, Bachchan was getting appreciated by the film fraternity for being very professional and punctual.According to "Excellence - The Amitabh Bachchan Way" by Virender Kapoor, Rajesh Khanna didn't react well to this."He apparently said in an interview that he believed that clerks were punctual and that he was not a clerk, but an artist," says the book.During this time, Bachchan was still emerging as a star and had just begun receiving appreciation from the public."Bragging about his position, he added that he was not a slave of his moods but instead, his moods were his slaves," it adds.Bachchan, however, not just remained respectful to Khanna but also admitted that the latter would always be the only superstar for him.Bachchan was highly impressed by the fact that the late actor had appeared in 153 films by 1991, in a span of 25 years which included 101 solo and 21 multi-star-cast films.He was in awe of Khanna's immense hard work and respected that despite having three films releasing every year, he had managed to give 95 jubilee hits.But later, in a way, he replaced Khanna becoming the 'Angry Young Man of Bollywood'."In an interview, however, Bachchan confessed that he had never expected to play lead roles. He always thought he was not conventionally good-looking and felt that he would never look as good as Rajesh Khanna," the book says.The book reveals Bachchan, seeing Khanna's photos in Filmfare, often wondered "'Yaar, ye aadmi kya khaata hai? Iske gaal itne lal kaise hain?' (What does this man eat? How are his cheeks so red?)"Despite being two of the leading actors in Bollywood, Amitabh Bachchan in a rare interview had revealed that the duo never "bickered, argued or tried to upstage one another in any manner" on the sets of "Anand" or "Namak Haraam".On the contrary, when Bachchan was working in Calcutta (now Kolkata) and was keen to join films, his inspiration was Khanna.He recalled how happy he had been when Hrishikesh Mukherjee asked him to work with Rajesh Khanna in "Anand". "It was a dream come true" for him.Bachchan remained a modest admirer of the late actor throughout his career as he would always admit his fame was purely because he was working with Khanna.And the admiration wasn't one-sided.After seeing Bachchan in "Namak Haraam" at a trial at Liberty cinema, Khanna knew his time was up."'Here is the superstar of tomorrow,' he had told Hrishikesh Mukherjee.""Excellence - The Amitabh Bachchan Way", a biographical work on Bachchan by Rupa publications, releases today, on his 75th birthday.