Catwoman

No — it is a standalone young adult novel set in the DC Universe, published as part of the DC Icons series in which different YA authors reimagined DC characters. It shares no continuity with Maas's Throne of Glass, ACOTAR, or Crescent City universes.

DC Icons was a YA anthology initiative in which prominent young adult authors wrote standalone novels reimagining DC Comics characters. Other entries include Wonder Woman: Warbringer by Leigh Bardugo, Batman: Nightwalker by Marie Lu, and Superman: Dawnbreaker by Matt de la Peña. Catwoman: Soulstealer (2018) was Maas's contribution.

It was designed to work for both audiences. Familiarity with Catwoman and Gotham adds context but is not required — Maas presents a self-contained reimagining that establishes its own version of the character. Maas fans may notice familiar dynamics (morally complex protagonist, slow-burn antagonist relationship, found-family elements), though the tone is lighter than her fantasy work.

Yes — this is the most age-appropriate of Maas's publications. The violence and romantic content are kept firmly within standard YA parameters. It is notably less dark than the later entries in her fantasy series, and was explicitly aimed at the younger end of the YA demographic as part of the DC Icons initiative.

Luke Fox as Batwing exists in DC comics continuity, where he was introduced as the successor to the original Batwing. The version in Catwoman: Soulstealer is a reimagining for the Icons series and does not follow comics continuity strictly — Maas adapted the character to serve the story's purposes rather than staying faithful to existing DC lore.