Niven is an uncommonly occurring given name for males but a very prominent surname for both adults and children (#19272 out of 150436, Top 13%). (2000 U.S. Census). Shown below is the baby name popularity of Niven for boys.
So, what length is the right one for a book? The average nonfiction book, if such a thing exists, runs about 50,000 to 75,000 words, but this can vary depending upon category. Biographies, for example, can run 200,000 words.
For paperbacks you get 25-50 lines per page, with 35 being a good average. This line count includes blank lines between paragraphs as well as lines with just a single word. At one extreme you get large print books with 250 words on the page. Academic books might put 600 words on a page with works of reference squeezing in 1000 words. A good working average is 400.