Reddit mentions of Relativity: A Very Short Introduction

You should look into the [Very Short Introduction] (http://www.oup.com/us/catalog/general/series/VeryShortIntroductions/ series) series. About 342 books that are all in the range of 100 to 200 pages. They cover anything from [History] (http://www.amazon.com/History-Introduction-John-H-Arnold/dp/019285352X/ref=sr_1_2?s=books&ie=UTF8&qid=1346605671&sr=1-2&keywords=a+very+short+introduction) to [Mathematics] (http://www.amazon.com/Mathematics-Short-Introduction-Timothy-Gowers/dp/0192853619/ref=sr_1_4?s=books&ie=UTF8&qid=1346605671&sr=1-4&keywords=a+very+short+introduction) and even really specific topics like [Relativity] (http://www.amazon.com/Relativity-Short-Introduction-Russell-Stannard/dp/0199236224/ref=sr_1_15?s=books&ie=UTF8&qid=1346605803&sr=1-15&keywords=a+very+short+introduction). It's a gold mine of information and the best part is that all of the books are usually under $10.00's. They're perfect for what you're looking for.

Any decent introduction to special relativity should cover it. I don't know how technical you are, though. If you're mathematically inclined, Taylor and Wheeler's Spacetime Physics is an awesome book. A lot cheaper and pretty accessible would be Relativity: A Very Short Introduction

The Feynman Lectures are a perfect introduction to physics from high school level all the way up to degree level.

A good understanding of maths is essential to more advanced physics and there is an excellent textbook written by two extremely qualified headmaster's called The Language Of Physics: A Foundation for University Study which is what's recommended to first year University students and poses questions at the end of each chapter.

If you're looking for something a little less intimidating, then the A Very Short Introduction series have a perfect range of short (and cheap!) books on Physics: [Quantum Theory]
(https://www.amazon.co.uk/gp/product/0192802526/ref=pd_sim_14_4?ie=UTF8&psc=1&refRID=9A3MSV2XSQRYF880MYP6), Relativity, Particle Physics, Cosmology, Nuclear Physics, Black Holes, Thermodynamics, Astrophysics, Light and Magnetism. These are great little books that don't blow your head off!

Physics is an extremely interesting subject to read around and I wish you the best with it :)