The story of this group of subatomic particles, believed to be among the fundamental constituents of matter, is explained in this illuminating book. Written in high/low text with color illustrations and historic photos, this new title explains the quark’s unique makeup and how protons and electrons are made up of quarks.
Maybe a bit too much history, assumes a bit more than middle-school physics, but gets to the meat of modern physics and clearly explained. Much of the history is a repeat of what is in The Electron, so I'd skip that one if favor of The Quark.