Pretty decent spin on the a-b-o trope; nothing new added but the combination of elements isn't something I've seen in one omegaverse title yet (until now).
In short, an enjoyable, light read with just enough drama and fluff and a pinch of emotional turmoil.
Specific omegaverse details may vary from title to title, but one of the basics is that male/female omegas experience a heat period and are exponentially the most fertile. By comparison, normal females and males are considered betas and don't experience heat.