The Lightning Thief received mostly positive reviews. The book has a rating of 4.24 out of 5 on Goodreads. Common Sense Media said, "There are two levels of fun in The Lightning Thief. One is the fast-paced quest of a young hero and his friends to save the world..." and added, "Another level of fun here – laughing at the wicked ways the author has updated the gods and monsters for the 21st century". However, it did criticize some aspects of the book, describing the prose as "choppy and attitude-filled" and complaining that "[t]he characters aren't emotionally involving". Its overall rating was 4 stars out of 5. Numerous other reviews were more positive. The New York Times praised The Lightning Thief as "perfectly paced, with electrifying moments chasing each other like heartbeats". School Library Journal said in its starred review that the book was "[a]n adventure-quest with a hip edge" and that "[r]eaders will be eager to follow the young protagonist's next move". Kirkus Reviews reviews said, "The sardonic tone of the narrator's voice lends a refreshing air of realism to this riotously paced quest tale of heroism that questions the realities of our world, family, friendship and loyalty." Eoin Colfer, author of Artemis Fowl called it "A fantastic blend of myth and modern". Finally, Publishers Weekly also praised the book, regarding it as "swift and humorous" and added that the book would "leave many readers eager for the next installment."
On April 8, 2007, The Lightning Thief was ranked ninth on The New York Times Best Seller list for children's books. The Lightning Thief was the winner of the School Library Journal Best Book of 2005 as well one of the books in the Chicago Public Library Best of the Best Books List, 2005. It was also in the VOYA Top Shelf Fiction List and was the winner of the Red House Children's Book Award Winner (UK), 2006; Askews Torchlight Award (UK), 2006; and the Mark Twain Award (Missouri Association of School Librarians), 2008. It was an American Library Association Notable Book, 2006 and a New York Times Notable Book (2005). It received the Young Reader's Choice Award in 2008 and the Rebecca Caudill Young Reader's Book Award in 2009. Scholastic Parent & Child magazine also included the novel within its 100 "Greatest Books for Kids." When asked about the various awards, Rick Riordan said: "The ultimate compliment for a children's writer is when the kids like it."