If lost or destroyed, a new copy can be obtained from the bookcase in your Player-Owned House made through Construction.
Below is the text you can read from within the book.
The Cadarn family is one of the oldest elf clan names. Able to trace its blood line back to one of the eight families brought here by Seren in the First Age, it was the Cadarn's responsibility to protect the other seven clans from any hostility encountered while colonising this new world.
Not much is known about the first generations of elves to walk this land. The only remaining documentation is the ancestry records. It's not until the start of the Third Age that we find surviving transcripts, and these are few and far between.
In the Third Age there was constant battling between the different gods and their followers. The need for protection in these troubled times made the Cadarn clan one of the most powerful in the elven domain.
After centuries of fighting, the war finally ended when the gods realised that they would destroy the very thing they were fighting over. The gods chose to agree on a pact of non-influence. With no great threat left, the Cadarn clan found that their skills were of little use in Tirannwn.
At the start of the Fourth Age the Cadarn family spearheaded an expansion into the lands east of Arandar. The occupation lasted for several centuries, before its final collapse near the end of the Fourth Age. With the death of Baxtorian Cadarn, and his sons not yet of age to rule, the elven clan returned to Tirannwn leaderless. The Cadarn clan lost much standing within the elven council in this time. This led to a cessation of all exploits within the land to the east, and the eventual closure of all routes through Arandar.