You absolutely must read Footfall by Niven and Pournelle - It's one of the best alien invasion novels ever written imo. The destruction of the Hoover Dam, the Kansas Jayhawks, a mothership of massive size, meteor attacks, lasers, weird-shaped aliens, AND the nuclear powered ship - it's all there, and in absolutely gripping and believable detail too... a truly epic scifi novel and a mere 700 pages...