I would like to recommend people who would like to know how the RFID works and how to built in your some electrical projects. This book, "Getting Started with RFID" is very concise, easy to read, and includes very practical description of wiring, programing, and controlling devices.
The author excuses this is an excerpt from the previous version (1st revision) of famous book "Getting Things Talk" from O'Reilly Media, because the current (2nd) revision replaces the article for RFID into the cutting edge technology - NFC (Near-Field Communication) which is adopted to such as Samsung's Galaxy Nexsus S, etc.
However, this book is still have a value for learners or hackers who want to implement not-so-complicated projects such as the same as familiar applications on a token of transportation systems. Yes, every IC tokens as an ticket for some countries' local trains are still not an NFC but this kind of simple RFIDs. Maybe, some leading countries in transportation systems such as England, Korea, and Japan adopt "non-contact type IC cards", but they may still be not an NFC (I am Japanese, and IC cards available in Japan nation wide is the SONY's "FeliCa" which is slightly different from NFC and it does not have compatibility with it, sigh...).
This book describes how to utilize the Parallax's RFID reader and devices with your project by using some very concrete and highly readable example programs written in Processing and Arduino. But, because this reader only send the unique ID of each RFID device from TTL-level serial data, any programming languages that can handle serial stream are applicable. Not only this virtue, but the conscious comments on every example codes leads the readers; both novice and expert programmer convince why every specific instructions are put there as so.
Consequently, this book is a handy primer for everyone who have an interesting to utilize RFID technology. I would recommend it.