Hi! I have just joined the group and this is my first post, but I have been a jazz fan for over half a century, which gives you an idea of my age (what was called modern jazz when I was young has been called classic jazz for quite a while!)
I recently purchased several box sets of European origin -- 4-disc sets and 10-disc ones. The best thing that can be said about some of them, especially the membran products, is that they are cheap. The worst ever is a ten-disc Thelonious Monk set that comes without a booklet or any personnel or recording dates information whatsoever except for a list of song titles on the back of each sleeve -- and some of those titles are wrong (also, you'll learn that "Smoke Gets in Your Eyes" was written by Monk!) As for contents, Discs #8 and #9 are particularly weird. On #8, Track 6 is identified as "More Than You Know" but is a different tune (I forget which), and Track 7 is not a Monk recording at all (it's "There Are Such Things" from the December 2, 1955 Rollins quartet session with Ray Bryant on piano). Then on Disc #8 we have most of the famous Miles Davis December 24, 1954 session , but what is identified on the sleeve as "Swing Spring" turns out to be the version of "Surrey With the Fringe on top" from Miles Davis's May 11, 1956 session with Red Garland, not Monk, on piano. (coincidentally, Miles quotes "Surrey" at the beginning of his second solo on "Swing Spring." Could there be a relation?) Oh yes, and Disc #10 is called "Friends play Monk" but they don't tell you who those friends are. Good for blindfold tests I guess..
I also got two Quadromania sets. The Milt Jackson one, called "La Ronde Suite," is interesting but the discography is weird. Membran has included the contents of "Concorde" and "Django" -- the most famous of the MJQ early LPs -- but instead of personnel and dates just mentioned in the discography booklet: "No detailed information available"!...A Barney Kessel Quadromania is pleasant enough, but half of Disc 3 and several cuts of Disc 4 are not Kessel but an obscure rhythm guitarist called Al Hendrickson, who I was not eager to discover.
Of course the major problem with those boxes is that you don't know what's in them until you buy. And you get what you pay for.