Reddit mentions of Transformers: The Ultimate Guide

You first have to decide which continuity you are most interested in. There's old school G1 that started back in 1984 (which itself is at least two different continuities, the cartoon and the comic book. Three if you count the UK comics.) There's the Cybertron series that your Starscream is from which is part of the Unicron trilogy. And there's the Bay-formers movies. While the first two have a little in common, the movie franchise has almost nothing in common with the rest of them other than the basic concept for a few characters. If you're only concerned with the movies, watching the previous 4 is an easy endeavor. If you really want to know more about the lore/history associated with the entire brand, that's a much greater task.

Two possibilties: Dive in to http://tfwiki.net/wiki/Continuities, and don't be afraid to just start link clicking until you've got a feel for how all the different continuities are related to one another.

The other possibility: Though a bit dated, the Ultimate Transformers Guide is a very good jumping off point: https://www.amazon.com/Transformers-Ultimate-Guide-Simon-Furman/dp/0756603145 It's a little G1 centric, but G1 serves as the basis for just about every other continuity.

So not this or this?