An inoffensive Monday puzzle. I appreciate the "keep it simple" theme and the elegant, central revealer (CANDY (33D: Checkout counter staple … or, when read as three words, what 20-, 31-, 47-, and 55- Across have in common)) that connects two of the theme answers.
19A: Mechanical man (ROBOT) is a nice clue, and I like the echo of the Sunday puzzle in 3D: "Double, double, ____ and trouble" (TOIL). I also like how that clue is symmetrical with 58D: Shakespearean king (LEAR). Nice little detail, there. And one more little detail that I like is the clue for PIA. Mr. Dobbin could have just gone with a simple "____ Zadora," and anyone who has ever done a crossword would have gotten it immediately, but he adds a somewhat ridiculous detail, and instead gives "40D: Zadora of "Santa Claus Conquers the Martians." We still get it immediately, but it's more fun this way.
There's not a whole lot more to call out, but that includes both good and bad details. In short, it's a solid Monday offering.