Although nothing would ever come close to Percy Jackson, if you're into Greek/Roman mythology and stories based on that, the books by John C. Wright are very good. They are a bit more adult than the Percy Jackson books, and you would have to have a good gist of most of the myths to understand certain parts, but I found (one of) them really good. I'm now on my way to reading the rest of the series! They not only have the Olympians, but they also have the Titans and the Phaeciaans (from the Odyssey). I would strongly recommend them if you're interested in reading more Percy Jackson while we all wait for The Son of Neptune!!!
I finished the series a couple of days ago: AMAZING. It turns out Zeus is dead, and the rest of the gods took children of chaos as hostages for the peace treaty. This has given me another idea : What do you think would happen if Zeus died?
I've been trying to find out how he die, by I can't find it specifically saying. I think three of his children gang up on him and hand him over to the titans (Athena, Hermes and ??), but I don't really know. If anyone reads it and comes across the answer, feel free to let everyone know!!!