Click
here for an excellent (and I mean excellent!) NEC history. Micheal there has documented what became the NEC back to
1881.
As for who has the 'oldest' code book, that's a subject of debate, as what would constitute a 'code book'. The NFPA didn't publish it until 1925. The oldest actual codebook I have is the 1911, my 1897 being the same 1984 reprint kbsparky has, and my 1896 and 1901 and handbooks.
The oldest genuine electrical book I have is "Munro and Jamieson's Pocket Book of Electrical Rules & Tables," printed in London in 1888.
Now, if you want old, try to find a copy of
The Nature and Property of Electricity, printed in England in 1746.