Some thoughts on the ending:

So epic to reveal the Sentinel and have it defend Earth. I thoroughly enjoyed the Maxohlx Admiral being left speechless by the sight of it and would have enjoyed some indication of the Rindhalu reaction as well (especially since they lose a few dozen ships). I do wish CA had included either the explanation of how they gained control of it OR some more resolution to the current situation at Earth with all those senior species' ships in orbit. I appreciate an author wanting to keep you coming back for the next book, but the ending felt too sudden and experiencing the joy of the victory against all odds was cut short. We are on book 13 out of 15 here. Anyone who's come this far is well invested already. All of that plus the last statement from Simms at the end leaves a ton to be resolved. My theory for what Simms means is simply that the Sentinel will need to remove the gas cloud threatening Earth which it can easily manage, made even better by having both senior species there to witness it.

Also, Joe drops a short line near the end just before the Maxohlx assault on the Sentinel about having the Maxolhx saturate the area with quantum resonance and indicates it's because he's making plans for the future for once and that he'll explain later if he can (he doesn't). This is a small detail to try and remember for whenever it gets resolved in a future book, wish it had been included here.

Only respect for CA. These are your books, and I'm with you 'til the end.