At Amazon.com, the CD
Power Klingon (1996, on
cassette too) is more complete than the older cassette
Conversational Klingon (1992). I haven't been able to find study guides for the GRE's or the certification tests, so the
Klingon-English Dictionary and the essential
Klingon for the Galactic Traveler will have to suffice for everyday use.
For more appreciation of the culture and context, try
The Klingon Way: A Warrior's Guide. "The proverbs are presented in tlhIngan Hol and DIvI' Hol (Klingon and English), along with a paragraph or two discussing the cultural background, and occasional grammatical tips".
Or try the more fluffy and diplomatic
Star Trek Cookbook but understand "qoH vuvbe' SuS" ("The wind does not respect a fool"). They also have more mundane volumes on
religion,
ethics,
computers,
physics,
star charts, and so on -- some quite good, some not very accurate.
The Encyclopedia is about all you need there.
The
Klingon Language Institute has recently restored the original version of
Hamlet, Prince of Denmark but you can find both English and Klingon side by side in the more versatile
The Klingon Hamlet, which has received excellent reviews.
"For too long, readers throughout the Federation have been exposed to The Tragedy of Khamlet, Son of the Emperor of Qo'nos, that classic work of Klingon literature, only through inadequate and misleading English translations. Now at last, thanks to the tireless efforts of the Klingon Language Institute, this powerful drama by the legendary Klingon playwright, Wil'yam Shex'pir, can be appreciated in the elegance and glory of its original tongue."
Any number of ways to appreciate their literature, art and culture, enjoy the journey, and get ahead in your job too. Just some helpful tips!
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"A warrior fights to the death." Qapla'!