Actually it will be 18 full days if you don't count the arrival and departure day.
When I first picked up Rick's book I was sure I could see it all in 21 days, but I have since realized it would have been too whirlwind for my taste. And I didn't want to rent a car the entire time.
After weeks of thinking and plotting and contemplating, my latest draft ittinerary is as follows:
Fly into Venice
4 nights in Venice
Train to Florence 2:21 enroute
4 nights in Florence
Train to Pisa on the way out for short visit.
Train to Follonica to pick up ride to Maremma (car? taxi?)
3 nights in Maremma with 2 full days of horse trekking
Train to Rome
4 nights in Rome
Train to Amalfi
3 nights in Ravello Mare
Fly home from Napoli
Does anything think 4 days in Rome of Venice is unnecessary?
What about skipping Cinque Terra and opting for Amalfi?