This is a series of messages from an extraterrestrial entity named Ashtar, purportedly transmitted via 'automatic writing.' Ashtar was apparently channeled by Ethel P. Hill, an early UFO contactee. Ashtar claims to be the commander of a vast army of spacemen. He apparently reports directly to Jesus Christ, who, it is implied, will return at some point in a UFO.
Ashtar is a desultory speller, and sometimes slips into a bogus King James Bible-style English. One giveaway is his use of the word 'thyselves,' a neologism based on 'thyself.' The correct form of the second person plural possessive has been 'yourselves' since Old English.
Ashtar's message is both reassuring and vaguely terrifying. His constant reassurances that he has come (or will come, 'real soon now') to fix our problems, not to conquer, only deepen the concern.
This was first published circa 1957. It is now a classic work in the UFO genre.