Hey Elf,
I bought one or two Klingefuss frequency list books WAY (WAY !) back in the day. What a GREAT resource - at that time.
IMHO, things on shortwave have changed radically. There seems to be FAR less "utility" type stations ( maritime ARQ, RTTY , military voice, etc, etc .) on air now.
Frequency lists (in print or online) are a big asset -IF- they are derived actual on air monitoring and are up to date.
Even "WAY back when" , such lists were maybe 70% + of dead frequencies, that for whatever reason, you heard nothing . Ever. But what you DID hear was so cool that these occasional "nuggets" made the cost worthwhile. When I was at CSS/NSA Germany ( and at other locations I worked at ) , I actually found some of my installations active frequencies on such lists .That was a REAL hoot !
IF a RECENT copy of Klingesfuss is available for "medium " money then "maybe". He did a LOT of work to compile it and therefore, as I recall it , his book was not inexpensive, even back 30 or more years when I bought mine.
I USED to keep his books ,also Passport books and the lists from "murky" sources in Pop Comm ads ( etc) well beyond when I bought them, really just recall fond memories of things I USED to hear (tropical broadcast stations and long gone utilities, etc).
After 10 or 15 years of keeping them , I finally "let them go".
I still keep a few "short" handwritten frequency lists and info for stations (lifted from the WWW) that have been off air for up to 100 years , purely as a "historical archive " of what was one out there.
Again , I had a huge admiration for all of his hard work and certainly do not want to do anything to keep him from getting a sale.
I do not have any big outdoor antennas anymore . But if I did and I was hunting for such activity , I'd try and get a general idea of where any remaining stations might "hang out" and also take the time of day and state of current propagation into mind. Then I would just look on an SDR.
A while back I found a few "Buzz Saw" bursts (presumed US military - Any one know for sure ?) - at upper HF on this site's SDR. Not sure how much you'd find or how long it would take , but that's the way I would (me) roll now .The military UHF aero band would be my area of choice to look now . I think there "could" be more activity there now (in OPEN MODE !) than on HF ( maybe ).
A zillion years ago the best thing I ever got was a voice operated tape recordings from my scanner ( a really "primitive" attempt ). I'd leave up for days and then play it back. Of course there was no date/time stamp and I didn't even know which frequencies were actually recorded , but still kind of cool and better than nothing.
I also did a bit of UHF mil sat listening , got some stuff , but not a serious or long term effort on my part.
Again , just my two cents , but your call.
K