Several official eBooks and PDFs for GURPS 3rd Edition are distributed for free to support players:
A 32-page "distillation" of the core rules, ideal for introducing new players. GURPS 3rd Edition eBooks
While (often referred to as "GURPS Classic" by its publisher) has been superseded by the 4th Edition, a significant portion of its library is officially available in digital eBook formats. Current Availability & Digital Distribution Several official eBooks and PDFs for GURPS 3rd
Many 3rd Edition supplements—including genre worldbooks like GURPS Japan and GURPS Espionage —have been converted into digital reprints known as the e23 project . GURPS 3rd Edition eBooks