Transformers also had a long-running comic series printed by Marvel Comics, which aficionados will assure you presented the *true* storyline, rather than the twisted version presented by the cartoons ;)
It's a long time since I read them and, sadly, I don't believe I have my collection anymore (lost due to being left in my parents' house).
There were a variety of different "groups" evolved at various points in the storyline, to introduce new characters over and above the original "core". Such as the Dinobots, Headmasters, Powermasters etc.
Plus some of the robots were damn cool in their own right, such as Shockwave ("logic dictates X, but emotion says Y!"), Soundwave (who used to run the letters page, referred to humans as Carbon-based units, and said (ptui!) a lot).
And some incidental characters were damn cool, especially Unicron, who is featured in the movie, and Death's Head who is didn't but was exceptionally cool.