Ralph 124C 41 : A Romance Of The Year 2660 by Hugo Gernsback. The Stratford Company, 1925. Cover by Frank R. Paul.
Gernsback is better known for his magazines and his inventions, but his novel (first published in 1911) is genuinely interesting. Like his magazines it's crammed full of future predictions - television, videophones, tape recorders, radar, synthetic clothes, solar energy, space flight.
Alas it's not that well written. It's a plodding melodrama and critics have been very unkind to it. But it is a landmark in American science fiction and if you can get past the endless exposition it's a fascinating read. The 'future' really was first codified in the Edwardian age.