1] Taylor and Wheeler, _Spacetime Physics_
Still the best introduction out there.  

2] "Relativity" :  Einstein's popular exposition.

3] Wolfgang Rindler, Essential Relativity. Springer 1977
With a heavy bias towards astrophysics and therefore on a more 
moderate level formally. Quite strong on intuition.

4] A P French: Special Relativity
A through introductory text.  Good discussion of the twin
paradox, pole and the barn etc.  Plenty of diagrams
illustrating lorentz transformed co-ordinates, giving both an
algebraic and geometrical insight to SR.

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