The Aparo and Fleisher Spectre was directly rooted in the brutal (and often almost childlike) original Spectre as created by Jerry Siegel (he of Superman creation fame) and artist Bernard Bailey. The original series began in February 1940 in More Fun Comics #52.
Probably only Aparo's work on Batman supercedes his fame in comics circles for doing The Spectre with Michael Fleisher for a short run in Adventure Comics in the 1970s.
Batman 291 cover with Catwoman
Brave and the Bold 105 - Batman and Wonder Woman
Brave and the Bold 107 - Black and White Page
Brave and the Bold 109 Cover - Batman and the Demon
Brave and the Bold 111 Cover - Batman and the Joker
Brave and the Bold 111 splash page
Brave and the Bold 111 Page 14 - Joker and the Gates of Fear
Brave and the Bold Manbat - Issue 117 - Cover - Batman and Manbat
Brave and the Bold Manbat - Issue 117 - Page 5
Brave and the Bold Manbat - Issue 117 - page 6
Brave and the Bold Manbat - Issue 117 - page 17 - Manbat
Brave and the Bold 178 - Batman and the Creeper
Brave and the Bold 160 - Supergirl
Detective Comics 444 - Cover - Bat-Murderer
The Spectre from Adventure Comics 431
The Spectre from Adventure Comics 431 - The Valley of Death
New Jim Aparo collection coming from DC Comics. Hope it includes the run of Archie Goodwin-penned tales form the mid-seventies. Cover of the book (as advertised so far) is a recoloring of the art Aparo did for the cover of Brave and the Bold 111. See it at 1400 pixels here.