As a suggestion for Toni, who asked about a possible book to read about
quarks, I would highly recommend the book "Quarks" by Y. Nambu. It is a
very good presentation of particle physics at a nontechnical level.
Earlier this month Nambu was awarded the Nobel Prize in Physics for his
work on spontaneously broken symmetry. This was done around 1960, and
this too is explained in his book.