One of the better books on the UFO phenomenon available at a reasonable price right now is Jerry Clark's Strange Skies: Pilot Encounters with UFOs (New York: Citadel Press Books, 2003).
Strange Skies is a measured and balanced book that takes time to expose clearly fraudulent cases, like Maury Island, and note those which have been explained, like the Mantell case, before moving on to the still unexplained cases which, as the title suggests, center on pilot sightings. Among those included by Clark are the RB-47 case (pp. 191 - 194), which would certainly rate on my personal Top 10 list of top cases ever, but which is largely unknown, even by some ufologists.
Clark's writing is crisp, engaging and to the point. Most important, he gets at the crux of the problem with UFO debunkers, like Phil Klass, who dismiss the phenomenon out of hand (as opposed to sceptics, who tend to proceed on a case by case basis). He echoes J. Allen Hynek (see "J. Allen Hynek: Not an Aplogist Ufologist), when he writes, at p. 216:
"If UFOs do not exist as genuine anomolies, one would expect that high strangeness reports of, for example, structured discs - the ostensible product of intelligent manufacture and control - would come overwhelmingly from unreliable - that is, naive, dishonest, or emotionally disturbed - witnesses... The opposite happens to be true. As this book, for but one example, has shown, there are plenty of reports that are both credible and interesting. An impressive number have come from military and civilian pilots, whose very survival depends on their being able to make sound assessments of what they are seeing in their airspace. In the early 1950s, a study conducted for Project Blue Book by the civilian Battelle Institute revealed that the best reports came from the most qualified observers, the poorest from the least qualified. Moreover, the best sightings were the most difficult to explain and the ones of the longest duration, affording observers a better chance of figuring out what they were or were not seeing. Battelle's analysis showed that reports of (in Blue Book's terminology) 'knowns' and 'unknowns' were fundamentally unalike. In other words, what we call unidentified flying objects are most unlikely to be identified flying objects in the waiting."
One does not have to accept that every case presented by Clark in Strange Skies is a genuine UFO (some may indeed be IFOs that remain unexplained) to understand that this is a phenomenon with excellent sightings by solid witnesses that demands, as a result, more serious study.
Clocking in at a user-friendly 254 pages and USD $16.95 price tag, Strange Skies: Pilot Encounters with UFOs is a must read for both the dedicated ufologist and the casual reader, and marks another positive contribution to the study of the UFO phenomenon from a man who has made more than his share over the years.