Mythological gods are all symbols or personifications of particular attributes or phenomena. Aphrodite is the god of love, and so she symbolizes (wait for it) love. Hephaestus is the god of fire, so he symbolizes fire. Gaea is the god of earth so she personifies the earth. Khione is the evil god of snow, so snow and snowstorms and frost in the novel are bad. This is not complex magic-robot-dragon rocket science here people.
That doesn't mean ancient Greek myths were simple. On the contrary, they could be weird and complicated and intricate, filled with jealousy and passion and twisted motivations. The Medea story, in which she betrayed her father for the sake of Jason of the Argonauts and then eventually got mad at him and killed her own children, is a nasty and convoluted tale, and just one example of the wild and crazy world of Greek mythology.
But The Lost Hero isn't the tale of the Golden Fleece or of the Trojan War. It's a straightforward adventure tale, where you root for the heroes to beat the monsters. And in this context, the Greek gods operate as fairly simple representations of the things they symbolize. Other symbols are similarly unsubtle: Leo's magic tool belt symbolizes his skill with machines, Midas's golden touch indicates his greed. Symbols, like the gods, aren't there to add mystery or ambiguity. Rather, they're there to lock information into place with a satisfying click. As you go along you get to claim each meaning the way that the gods claim their kids—unambiguously and on schedule, so you can go to the right cabin and know just how you fit in.