A link to all 12 issues of DC's 1973-1975 THE SHADOW run. I love the Robbins and Cruz issues as much as the Kaluta run.
Kaluta did 1-4 and 6.
Frank Robbins did art on 5, 7, 8, and 9.
E.R. Cruz did art on 10-12.

And no doubt, it was O'Neil's scripting of the entire series that gave it a consistency throughout the artist changes.
If I were going to do a collected hardcover, I'd also include a SHERLOCK HOLMES one-shot by O'Neil/Cruz that came out
about the same time as issue 12.
And I'd want to include JUSTICE INC (the Avenger) 1-4, out about the same time as issues 9-12, scripted by O'Neil, art by Al McWilliams
(issue 1), and Kirby (2-4). A logical inclusion because like THE SHADOW series, all were scripted by O'Neil, and because the Avenger
also appeared in SHADOW 11. Another 1930's pulp/crimefighting series.

Maybe followed by another hardcover of O'Neil and others' work on the Edgar Rice Burroughs adaptations from TARZAN 207-256,
KORAK 46-56 and WEIRD WORLDS with various writers and artists like Kaluta, Weiss, Adams, Anderson, Almendola, Morrow and
Chaykin.

Possibly followed by a SWORD OF SORCERY 1-5 collected reprint, that also collects work by O'Neil, Chaykin, Kaluta, Wrightson,
Simonson, and Adams (as Crusty Bunkers), and Starlin.
And maybe include Chaykin's Ironwulf stories from WEIRD WORLDS 8-10 to fill out the volume with more O'Neil/Chaykin material.

Beyond obvious picks like the O'Neil/Adams BATMAN and DETECTIVE runs, and their Green Lantern/Green Arrow run, O'Neil did a
ton of groundbreaking work that I'm amazed hasn't been reprinted yet.
Including a Swan/Anderson SUPERMAN run (233-246), and WONDER WOMAN 178-202, that had Zen-Bhuddist themes and was
interesting because Diana Prince had no superpowers, just her wits and some martial arts skills, that made an interesting break
from the regular series.