This review will contain spoilers!
In many sentences:
Rick Riordan has done it again, with another wildly entertaining Percy Jackson book. Even 5 books into the series, nothing has been lost. It still has the same great style with plenty of laugh out loud moments. Of all the books, this is by far the most action packed. From the moment they get to New York until Kronos is defeated, it is simply one outrageously entertaining fight after the other.
Fortunately, the book is not just its action moments. Riordan does an excellent job of tying up all the loose ends, answering all our questions, and even giving us what we want (Percy and Annabeth together) without breaking Rachel's heart. Though one could complain that everything ends up a little too perfect (a la the Twilight series), there are still several moments of sadness. Silena, through her betrayal of camp half-blood, feels she is the reason her boyfriend died. Furthermore, her own sacrifice to bring the Ares campers to the fight is sad. Ultimately, though, you don't read a Percy Jackson book expecting to be stricken with grief, and I am happy with Riordan's balance in this regard.
In the end, if you have enjoyed the series up to this point, there's no reason to not pick up the Last Olympian immediately. Even if you haven't read any of the books and I just gave away the ending, it's still worth picking up. The plot itself is only half the fun with Riordan's books (in fact, most of the plot is predictable considering it all stems from classic Greek mythology). The characters, their interaction, and the sly humor is really why I keep coming back again and again. I can only hope that his comment at the end about this being the "first Camp Half-Blood series" means we will soon be enjoying more Olympian adventures.
I'm not including a quote, not because there weren't some great and memorable moments, but just because I don't think they work very well out of context. So, I'll include two here: "There was little laughter at the camp these days. Even the Hermes cabin didn't play so many pranks. It's hard to enjoy practical jokes when your whole life feels like one" (46).
"Either way, I doubted we could stop the prophecy. A blade was supposed to reap my soul. As a general rule, I preferred not to have my soul reaped" (56).