Suggested Reading For Nepenthes
Nepenthes Of Borneo - Charles Clarke
Nepenthes Of Sumatra And Peninsular Malaysia - Charles Clarke
Pitcher Plants Of Borneo - Anthea Phillips & Anthony Lamb
The Savage Garden - Peter D'Amato
Nepenthes Of Mt. Kinabalu - Shigeo Kurata
A Skeletal Revision Of Nepenthes - Jebb & Cheek
For the most current information of published Nepenthes ranks and descriptions, I would recommend Jebb & Cheeks 1977 skeletal revision used in conjunction with Clarkes Nepenthes of Borneo. Clarke also has a new book due out at any time, and if he makes any changes, I would also recommend its use as well. I believe it is time to give less value to Danser's 1928 monograph. We have had significant field studies in the past two decades, and the lack of these field studies during Danser's time made his work much more difficult. Danser provided an invaluable service, but we have much more current resources available now, and these have been backed up by much more field research than we had in the early 1900's.
Nepenthaceae Of The Netherland Indies - B.
(This is the major monograph on Nepenthes written as a magazine article in 1928. It has been highly relied upon as the defacto work on Nepenthes until very recently (almost too highly relied upon) For serious research purposes, you should refer to this work. Seriously dated now, Danser's approach to classifying Nepenthes worked so well with the type of material he had to work with that most of the century passed until the next overhaul of the genus was written by Jebb & Cheek. There were sites on the internet where this could be downloaded, in which som eof the text was translated into English. As soon as I locate a site again, I'll list it here.
Recent works (from 1973 until today) have been published by the following people who have made extensive field studies of Nepenthes. These articles are normally published in scientific journals or magazines. I will try to list them at separately in the future, as some of the are publications of the descriptions of new species.