This book is the blueprint. Seeing or hearing the phrase "Look, I didn't want to be a half-blood" makes me froth at the mouth. This is the perfect introduction to the series; it sets the tone, introduces the basic worldbuiding, and builds up some amazing characters. This goes for all the books, but Percy is an incredibly likable protagonist that still has his flaws. His introduction is amazing, and we know from the start that he's a struggling kid that tries his best and comes to find himself as a demigod. The Lightning Thief is only the first book, but it has a great plot twist that has a ton of impact on the rest of the series, plotwise and emotionally. It's one of the best first books I've ever read, resolving things while still having that overarching plot to continue off of.