This book presents special relativity from first principles and logically arrives at the conclusions. There are simple diagrams and some thought experiments. Although the final form of the theory came to use Minkowski spaces and metric tensors, it is possible to discuss SR using nothing more than high school algebra.
That is the method used here in the first half of the book. That being said, the subject is open to a wide range of readers. For a more mathematically sophisticated treatment of the subject, please refer to the Advanced Text in the second part of the book.