Captain Edward Ruppelt's book The Report on Unidentified Flying Objects was first released in 1956. It contained lots solid of evidence in support of flying saucers' existence. However, the second, so-called expanded printing released in 1960 contained strange additional chapters that essentially debunked all the UFO evidence presented in the earlier chapters!
As far as I can remember, Major Donald Keyhoe first noted in one of his UFO books that something must have happened to "poor Ed", because Ruppelt's change of opinion seems totally unfounded and weird. It is my belief that the US government, with the aid of secret agents (perhaps something like "Men In Black"), forced Ruppelt to repent his first edition of The Report on Unidentified Flying Objects. The government then made Captain Ruppelt to label the whole UFO phenomenon as a "spage age myth".
In conclusion, I am quite sure the second edition has been released with the intention of covering up the truth about flying saucers. Consequently, I would say that only the first edition is really worth reading.
Kalevi Kolttonen