As a bibliophile, this article in the New York Times caught my eye today.
Yes, there are many academic books that "no one reads" and Newton's "Principia" may have been one of them, or may be not. Apparently there are 386 copies of the original printing in existence and a recent study published in the Annals of Science, available here, suggests that initial readership was much greater than previously understood. Of course, over time, this was one of the most influential scientific publications ever.
So, academicians, keep writing. as first prints may not always predict the impact of your work. The "immediacy index" of a publication can only go so far.
