Thanks for breaking this down! I thought the recent 80th anniversary deluxe for Green Lantern was kind of insultingly slim compared to the other character's volumes.In general, DC did a good job here. There are overlaps, but they are small, usually only four or five stories. The two Joker releases have an overlap of seven stories (140 pages), but considering that these books have 400+ pages, even this is still acceptable. Here's a list of all overlaps:
Superman - A Celebration Of 75 Years
Action Comics: 80 Years Of Superman (The Deluxe Edition)
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Action Comics #1: "Superman, Champion Of The Oppressed" (June 1938)
Action Comics #2: "Superman - Revolution In San Monte (Part II Of II)" (July 1938)
Action Comics #242: "Superman - The Super-Duel In Space" (July 1958)
Action Comics (Vol. 2) #0: "The Boy Who Stole Superman's Cape" (November 2012)
Batman - A Celebration Of 75 Years
Detective Comics: 80 Years Of Batman (The Deluxe Edition)
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Detective Comics #27: "The Bat-Man - The Case Of The Chemical Syndicate" (May 1939)
Detective Comics #327: "Batman - The Mystery Of The Menacing Mask!" (May 1964)
Detective Comics #359: "Batman - The Million Dollar Debut Of Batgirl!" (January 1967)
Detective Comics #474 (December 1977)
Detective Comics (Vol. 2) #27: "The Case Of The Chemical Syndicate" (March 2014)
The Joker - A Celebration Of 75 Years
The Joker: 80 Years Of The Clown Prince Of Crime (The Deluxe Edition)
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Batman #1: "The Joker" (June 1940)
Detective Comics #168: "Batman - The Man Behind The Red Hood!" (February 1951)
Batman #251 (September 1973)
Detective Comics #475 (February 1978)
Detective Comics #476 (April 1978)
Detective Comics #826 (February 2007)
Detective Comics (Vol. 2) #1 (November 2011)
The Flash - A Celebration Of 75 Years
The Flash: 80 Years Of The Fastest Man Alive (The Deluxe Edition)
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Flash Comics #1: "The Flash - Origin Of The Flash" (January 1940)
Showcase #4: "Mystery Of The Human Thunderbolt!" (October 1956)
The Flash #110: "Meet Kid Flash!" (January 1960)
The Flash #123 (September 1961)
The Flash #275 (July 1979)
Green Lantern - A Celebration Of 75 Years
Green Lantern: 80 Years Of The Emerald Knight (The Deluxe Edition)
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All-American Comics #16: "The Origin Of Green Lantern" (July 1940)
Green Lantern (Vol. 2) #59 (March 1968)
Green Lantern (Vol. 2) #87: "Beware My Power!" (December 1971)
Green Lantern (Vol. 3) #50 (March 1994)
Green Lantern Secret Files And Origins 2005: "Flight" (June 2005)