I'm planning to visit Loire valley and spend a week there. I know that I can travel from Paris to Tours by TGV, but I don't know what is the best way to explore the valley and visit individual castles. I don't need guided tours, I'm looking for a way to travel between the castles.
A car is definitely a must have to visit the Loire valley. You have independence, and you can find some beautiful castles and view the country.
But you can go to some castles by train from Tours. Here are some examples:
Chenonceaux: you can take the train from tours to Chenonceaux and walk to the castle. It can be beautiful because you have to cross the French garden.
Blois: can be reached by TER (= regional train)
Chambord: can be reached from Blois
Minibus is also a good option.
Tour Evasion ( the company I've traveled with ) has half-day tours ( two castles - approx 20-30 EUR ) and full-day tours ( four castles - approx 50 EUR ).
Entrance fees are not included, but the prices are reduced.