I must admit that I have but a passing interest in Theosophy. However, I am glad to see that people are keeping the knowledge alive. The New Age community of today seems to have forgotten this part of their past for the most part.
The following are the few other souces I know for books and collections on Theosophy, besides what has been presented in this thread. I can't speak for what authors are best to read and which to avoid, only that these links simply provide a plethora of books and articles to peruse
Internet Sacred Text Archive
https://www.sacred-texts.com/the/index.htm
Internet Archive (sorted by creator)
https://archive.org/details/texts?an...rSorter&page=2
Project Gutenberg
http://www.gutenberg.org/ebooks/sear..._order=titl e