As a child, I liked my superheroes to have a scientific bent, so the stories about physics grad student Ray (The Atom) Palmer adventuring not only on earth but also in time and other dimensional worlds appealed to me. Plus, kids can identify somewhat with a hero that the adult world towered over.
Comics from the '60s were all about gimmicks, and the Atom's was that he could shrink, varying from submicroscopic size to about a foot tall. That let stories develop from notions of putting the Atom in peril not only from normal-sized adults but also from various small objects, from the pointed hands of a watch to a Venus fly-trap to a draining sink (all represented here), which would then be drawn enticingly on the comic's cover.
Author Gardner Fox and artist Gil Kane had already gained some measure of fame for their work on Green Lantern, but they had yet to find their footing on The Atom. The Atom was never one of DC's most popular heroes, but I liked him, and this collection shows the two creators moving from the hero's origin to the establishment of recurring themes which would lead to The Atom's brief peak of popularity.
The collection includes the introduction of two villains who became favorites with DC Comics readers: Chronos the Time Thief (who used clock gimmicks) and Jason Woodrue the Plant-Master (not only a master gardener but also an exile from a dimension where dryads ruled). It also includes the first "Time Pool" stories, in which the Atom would use a wormhole in time (too small for normal humans) to make discoveries in the past. (Oddly, Chronos was never used in a Time Pool story, which would seem a natural combination.)
This book reprints Atom stories from SHOWCASE #s 34-36 and THE ATOM #s 1-5, 1961-1963.