Red Pyramid- Author Analysis

Rick Riordan has written three series of books so far: Percy Jackson, the Lost Hero, and the Red Pyramid (Not the series titles, but you get the gist). All of which have similar plot lines, very similar conflicts, characters, and, of course, various versions of ancient gods. Lastly, so I've heard, they will all be connected with a fourth series, which links the Egyptian series with the other two. Riordan is a great author, but I'm surprised that he is still going on with Greek and Roman gods. It takes enormous amounts of skill to be able to pull that off, but I think he will. Anyway, it seems that he is obsessed with ancient mythology, and I respect him for that. He also in two of the three series wrote about a single parent getting captured by the god of death, which I found quite interesting, but so far, I think it's working just fine.