Recommendations please: I want a book like Percy Jackson, or a theme like Narnia, where there’s war, mythical creatures etc

So to me, I've always been in love with Greek Mythology and wars (but not human wars, but I mean it could be involve but not just them) but it's hard to find books like that. I don't want just small skirmishes here and there, would love for it to be in a grand scale if possible. This being the case, please help me find a book I can use to get away from my phone.