Here is a site that will get you both of those delivered to your door for a total less than $12:
Byrne used book search
Byrne's books are the best introduction to carom written in English by a large margin. I think they will be all you need until your average at 3-cushion is over 0.50, when it might be time to think about more advanced books.
Recently Andreas Efler published three books on how to avoid (duck) kisses at 3-C, as an example of more advanced topics.
Walt Harris has four volumes on diamond systems, but Byrne covers many of them. Harris tends not to discuss details of the systems such as how they change for new cloth, so each system will be somewhat of a project to learn. If you decide to get the Harris books, go to the Harris site which is being maintained by a friend of Walt's. He has not yet figured out how to change the prices, so they are still at 2010 levels.
http://www.billiardsatlas.com/atlas.html