The first sentence presents a clear statement about book purchases, while the second sentence introduces a contrast regarding authors' profits. However, without additional context, it could be argued that the effectiveness of each sentence depends on what aspect you're focusing on.
If you're measuring effectiveness in terms of clarity and directness, the first sentence could be considered more effective since it states a straightforward fact. If you're looking at the effectiveness in terms of raising concern about authors’ profits, then the second sentence may resonate more.
Ultimately, I would lean towards "The first is more effective", as it communicates a clear fact without needing further elaboration.