I read it fast because I had quite some time to do so this week, but I can't say I liked it.
I still like the world of Greek and Roman gods and demi-gods. However, I felt this last book was so rushed that it lost all its flavour. Mostly I wasn't terribly convinced about the choice of POVs. OK, I liked seeing more of Nico's, but... Percy and Annabeth. Gods (pun totally intended). It was just as if they had become secondary characters, only here to be weakened and in trouble, without even a point of view of their own anymore. The other ones didn't exactly bring much either.
We also end with nice couples, er, everywhere. As if it was mandatory that everybody finds his/her partner at the end. Except that the spark wasn't here, as if, now that readers knew who was with who, there was no point in doing much with that anymore.
Speaking of which, the whole thing about Nico... In the previous book, I liked that he was being honest with his feelings, and I definitely hoped he wouldn't be the one character who dies because whatever mattered were the already-set couples. On the other hand, while having him
was nice, it was also dropped in there like a stone: artificial and not convincing. If only this had been handled differently...
Also, too many loose ends and details thrown under the carpet. For instance, we get a reminder of "Percy's fatal flaw", but it never really plays a part in the end. As for said ending, and the enemies in general, they were simply ridiculous and rushed through. You can't build up so much on Gaia waking up for four books, only to have everything end like it did.
So... Sorry, but that one was a serious disappointment for me.