Poorly made or unpopular movies may give the book bad publicity which would affect the sales and popularity of that book. Movie adaptations are viewed as representative/equal to the book. Therefore when a movie is deemed “not good” in the public opinion, that bad reputation can spread to the book as well. A movie adaptation could also spoil the reputation of a book for fans, not just the general public. Fans of the original book may see a poor adaptation and think to themselves, "That movie was awful. What was it again that I liked about the book? Maybe I didn't really like the book after all." Additionally, a movie adaptation does not even need to be a "bad movie" for the book's reputation to be altered. For instance, Howl's Moving Castle has a fairly similar plot to the original book, but it changes some of the traits of the main characters and some of the events that they participate in. As one example, the main character Sophie is very stubborn and blunt in the book, but in the movie she is mostly kind and agreeable. A few people who watched the movie before reading the book have commented on how unlikable she is in the book, and how her personality made them not want to read the book. Thus, even a much-loved adaptation may make a book's reputation worse if the book does not live up to the movie's standard, such as the main character being less likable.
Bad publicity is still publicity. If the movie adaptation is criticized, some may go to the original book to compare them and praise the book if they think it was better. For example, the movie adaptation of Percy Jackson and the Olympians: The Lightning Thief garnered tons of negative criticism when it was released. Many fans of the book and non-fan moviegoers alike thought the movie was a flop. However, after the movie was released, all five books in the Percy Jackson and the Olympians series were on the USA Today's best seller list in the Top 10. Thus, even a poor movie adaptation can increase public interest and grow the book's fan base.
[P1] One's opinion of a movie adaptation will impact their opinion of the original book. [C] Therefore, if a movie adaptation is not well-received, it will negatively impact the book. [P2] Even if a movie adaptation is well-received, it may be very different than the original book. [P3] If the book does not live up to the expectations of fans of the movie, then fans of the movie will be disappointed by the book. [P4] If fans of the movie are disappointed by the book, they may review the book negatively or otherwise negatively impact the book's reputation. [C] Therefore, if a movie adaptation is well-received but the book does not live up to the expectations of fans of the movie, then the adaptation can still have a negative impact on the book's reputation.
Rejecting the premises
[Rejecting P2] This is not bad for the book - all publicity is good publicity.