While editor Julius Schwartz used a lot of different writers at this point on the title, penciller Dick Dillin was a constant throughout. Indeed, JLA only had two different pencillers for the first 17 years or so of its existence, Mike Sekowsky and then Dillin. Dillin was solid, straightforward, and dependable -- so far as I know, he never missed a deadline, and he only left the book because he died (!).
He's "the" JLA artist for people of a certain age, an emblem of professionalism who knew how to tell a story, and could occasionally startle with some effects (here, he does some really interesting and memorable things with a wisp of smoke that gradually resolves itself into The Spectre over the course of an issue, as well as a fascinating couple of pages in which supervillain Libra expands while also losing all materiality). Also, Dillin's clean pencilling really looks good in the black-and-white Showcase format.
The stories are a lot of fun as well, with the post-Marvel psychology boom resulting in a certain amount of hand-wringing and soul-searching on the part of the Super Friends. Three unusual inter-universal crossovers appear, including a trip to Earth-X, where the Nazis won World War Two, and to Earth-2, the home of the Golden Age Justice Society which comes under attack by...a super-powered DC Comics writer named Cary Bates, previously of "our" Earth, Earth-Prime. Oh, Meta! All this, and Black Canary knits Red Tornado a new costume to replace the purple-and-red horror he'd been stuck with since his first appearance! Recommended.