"King's of the Buddha's Time" (1983) by Bhikkhu Amritananda of Nepal
(now deceased)
This is a really fantastic book that I would recommend to anyone
interested in Pali literature.
It is full of useful background information and puts Jataka stories
into context.
Often you hear names when reading the Tipitaka that can sometimes not
have meaning for the reader due to limitations in knowledge. This book
weaves together disparate parts of the Tipitaka into biographies and
narratives and provides this background info.
It only cost 80 baht (2.5 US dollars) at the bookstore across from Wat
Benjamapopit (sorry for spelling) which leads me to believe that the
price was set more to cover the cost of paper than to make any profit,
with an aim to disseminating this work as widely as possible.
Which leads me to conclude that a lot of authors of works probably
would be open to making their work available on the internet, if asked
politely with objective of non-profit dissemination made clear.