Why is Ready Player One movie so different from the book?

After reading the book and watching the movie, I found that some significant differences between them.

The novel version is more intense and complex as compare to movie. In the novel version, Wade was shown to very poor and have a small house as compare to the movie. In the novel, after Wade find the first key, he becomes bored and gives up to find the clue to get second key, but in the movie he never loses hope to find the second key.

The second difference I found out that where and how did Parzival (wade’s avatar) found the copper key. In the book, the first challenge (the one for the Copper Key) takes place on the planet Ludus, where all of the various in-OASIS schools are located, and requires players to journey to the middle of nowhere to play a large-scale version of the “Dungeons & Dragons” module “Tomb of Horrors.” Once that part of the challenge is beaten, the player must then defeat a D&D baddie at a game of “Joust.” But in the movie, Wade is the first person to complete that challenge by driving backwards in a race that was was not mentioned in the book, though he’s swiftly followed by Art3mis, and the pair rocket to the top of the Scoreboard to become the most famous people inside the OASIS.

Another main difference I found about Halliday and Morrow’s Background. Sorrento’s background might get a boost in the film, but Halliday and Morrow’s is vastly diminished. Introduced in the book as best friends since middle school, the novel delves into how their childhood friendship blossomed into a fruitful professional partnership in their older years. The eventual break between the pair serves as a both an alluring mystery and compelling piece of emotional information, but the film removes most of that backstory, instead focusing on their bond as adults. Those kid years? Never mentioned.