When Sinclair Ferguson spoke at Reformed Theological Seminary in Charlotte, NC a couple of years ago, he recounted that J.I. Packer’s modern evangelical classic, Knowing God, had an original print run of 2000 copies! Even then in 1973 Inter-Varsity Press (the book’s publisher) was fairly uncertain it could even sell all of the 2000 copies. Thank God they were wrong!
If you don’t have a copy, it’s available here.