I started watching the original series reruns about a year earlier (fall 1972) on a regular basis (mainly so I'd know how to act the role of Spock counterpointing my friend Kyle who liked playing Kirk). Sometime during that span, I began to enjoy the shows for their own sake.
Then in late August of 73, NBC started promoting its upcoming Saturday morning lineup and that's when Kyle and I learned Trek would premiere in animated format. CorporalCaptain reminded me of the preview special which I also watched. (For the younger members here, the "Big 3" networks, NBC, CBS and ABC used to run half hour previews of their new Saturday morning line-ups the Friday evening before they first aired.)
While the cartoon aired from September '73 through August of '75, reruns of the original series were suspended in our local market, Birmingham, Alabama. I can't remember if TOS ran on a competing affiliate. Point is, for those two years, TAS was the only Trek material available, so one watched it or simply did without. Not that it bothered me. For Kyle and I, it was Trek.
I purchased "Star Trek Log One" when it was first published as part of some release program. So I got the first several publications when they were first released.
In case you're wondering, no, I was not crazy about M'Ress at that time. Neither did I dislike her; she simply wasn't on my radar. (I wouldn't take note of her until late 1982 after I saw the movie "Cat People".) Spock was my "hero" since I roleplayed him. One thing that puzzled me was the lack of "frown lines" upon his animated visage. Even as a kid not quite 11 years old, I thought those creases were a defining attribute of Nimoy's face. But even then I appreciated the cartoon could depict far grander vistas and exotic flora and fauna than the live action could afford.