Whats the most well known 圣谕书?
The Sacred Edict 《聖諭》was first published by order of the Kangxi Emperor in 1670 (there were earlier works, but this was the first with this title). It was published in a revised and expanded version in 1724 by the Yongzheng Emperor called 《聖諭廣訓》There is an article on this in the Chinese Wikipedia.  There is also an article in the English Wikipedia under Sacred Edict of the Kangxi Emperor.

The Sacred Edict was a 'hortatory' work, meaning it 'urged people to do good' (勸善). There was a whole category of such books called 善書; you can still pick these up at Buddhist or Taoist temples in Taiwan.  I wouldn't call these books of fables, though.