The breakdown: Avatar: TLA is a slightly mature re-imagining that feels more like a suspenseful narrative driven novel than an "Adventure of the Week" Cartoon.
If you're looking for a live action clone then you may be disappointed, however if you enjoyed the darker elements of the original series found in Episodes like "The Boiling Rock" or "The Southern Raiders" then it might just be everything you hope for.
The new tone is set early as we're introduced to the beginning of the war, watching the fire Nations genocide of the Air Nomads in an attempt to stop the Avatar Cycle as an Airbender is next in line. For the first time we actually see a firebender kill someone in graphic awe.
The pacing feels a bit rushed when compared to the source material but when separating the two entities it feels on par for a serialized action/Drama.
The acting is mostly decent. Members of the fire nation steal every scene with proficiency. There's also an overall increased emphasis on the Fire Nation and its motives in Book 1, a change I found refreshing. Zuko, Iroh, Azula, and Ozai are all true to form.
GranGran and the Kyoshi warriors also really help emerse you in the different regions of their worlds and cultures.
While some of the development is rushed its far from absent and I look forward to Books 2 and 3, where the higher stakes found in the original series will be more on par with the tone of the Live action series.
The biggest con I would say is the acting of our main protagonist, Aangs delivery can feel a bit hallow and stalled at times, however as a child actor he's likely to get better in time and with development.