The Tripods Trilogy

Another juvenile series I enjoyed was the Tripods series by John Christopher.  I believe originally this was a trilogy, but it has expanded to 4 with the addition of a prequel.
The first book in the trilogy is where I will start. It’s The White Mountains. 
Aliens, The Tripods, have invaded and conquered the Earth some time ago.  Limited numbers of humans survived the destruction and killing.  They now live as virtual slaves of the Tripods as the aliens go about their mysterious business. 
Mainly the Tripds live in 3 cities where conditions of gravity, and so forth are closer to the Tripods requirements.
Humans do not question their situation, they are under the control of the Tripods and accept their lives.
But this is maintained by everyone being ‘capped’.  A metal device is fitted to your head and the Tripods can then control you. 
Will Parker is about to undergo the ceremony of being capped since he has come of age.  Youngsters are not capped until old enough.
So he still can have rebellious thoughts.  But not for long.
 Will becomes aware of the resistance to the Tripods and after various adventures decides to journey to The White Mountains where the resistance is apparently located. 
I thought this was a real good story when I read it way back when.  I have re-read it since.  A nice twist on alien invasions with young people, because of the lack of caps, being the lead in the resistance.  And some interesting writing about the society of humans living under the Tripods.  A pastoral society, one that does not question the domination of the aliens.  Reminds me of feudal society. 
Next in the trilogy The City of Gold and Lead.  In my next post.