One book I have not seen listed is
The Classic Cattleyas by AA Chadwick and Arthur Chadwick.
I cannot express how much I have enjoyed this book!
Not only is it an excellent "read" with vignettes of history regarding Cattleyas, it also goes into detail regarding the region and culture of each of the large flowering Cattleya species.
It is possibly the best "orchid reference book" I've ever read.
There are also chapters on disease, repotting, and even art as they relate to Cattleyas.
I still refer to it often and highly recommend it.
Witner's series is not easy to find and some of the volumes are very pricey! Especially Volume 3 which I have seen listed as high as $1800.
I got mine when a listing popped up for $40
Another book I recently bought on recommendation from this forum that I do not see listed here is
Moth Orchids: The Complete Guide to Phalaenopsis by Steven A Frowine. I have been very please with it thus far and it has inspired me to at least keep a few of these plants (since I love them so much) despite my previous poor luck with them. So far, so good