The IDW Transformers books are divided into two ongoing series - More Than Meets The Eye and Robots In Disguise. However, there was a digital-only series set in the early days of the epic war between the Autobots and Decepticons called Autocracy, and there were a 'annual issues for each series explaining the history of Cybertron and the mysterious giant Metrotitans.
Now, IDW is bringing back the "Spotlight" books, wherein one character out of the cast of hundreds is given center stage for a bit of historical context and character work, and the first one up is Thundercracker. When last we left him, he was on Earth - having left the Decepticons in disgust, but rebuffed the Autobots with disdain. This story, however, takes place in that distant past, post-Autocracy. The Spotlight books tend to create some confusion as far as the timeline goes, but they're great opportunities to elevate characters into... well, the spotlight.
Check out this preview of Transformers Spotlight: Thundercracker, due out tomorrow from RID writer John Barber and artist Chee.