If you’re interested in comics based on the show itself, check out the following:
-Batman Beyond (1999) #'s 1-6
The very first BB comic, issues 1 and 2 of this mini-series adapt the first two episodes of the show, then go into new stories for the remaining four issues.
-Batman Beyond (1999-2001)
The very first ongoing Batman Beyond series, this book, like the mini-series before it, ably captures the tone and spirit of the TV show.
If you’re wanting to jump right into
the Rebirth era of Batman Beyond, you can. Just know that it does reference some things that have occured in previous Batman Beyond/set in the future DCU titles.
The items of reference aren’t anything you need to know before starting the book. You can begin with the Batman Beyond Rebirth one-shot, then segue into the series very easily and still understand what’s going on just fine.
If you’re looking to expand your Batman Beyond experience, there are also series based on Superman and the Justice League from that timeframe. They are Superman Beyond, Justice League Beyond and Justice League Beyond 2.0.