I've read all four. Of the original three, The Flood definitly lagged. But keep in mind, The Flood was mainly about revealing what was happening everwhere else on Halo, not just what happened to Master Chief. Of the four out right now, I can't decide which is better, Fall of Reach or Ghosts of Onyx....
Anyway, certainly looking forward to Contact. And if anyone hasn't, definitely read all of the books. Ya gots to have the full story. It makes everything that much more enjoyable.