BACKGROUND: While the evidence base on web-based cancer misinformation continues to develop, relatively little is known about the extent of such information on the world's largest e-commerce website, Amazon. Multiple media reports indicate that Amazon may host on its platform questionable cancer-related products for sale, such as books on purported cancer cures. This context suggests an urgent need to evaluate Amazon.com for cancer misinformation. OBJECTIVE: This study sought to (1) examine to what extent are misleading cancer cure books for sale on Amazon.com and (2) determine how cancer cure books on Amazon.com provide misleading cancer information. METHODS: We searched "cancer cure" on Amazon.com and retrieved the top 1000 English-language book search results. We reviewed the books' descriptions and titles to determine whether the books provided misleading cancer cure or treatment information. We considered a book to be misleading if it suggested scientifically unsupported cancer treatment approaches to cure or meaningfully treat cancer. Among books coded as misleading, we conducted an inductive latent thematic analysis to determine the informational value the books sought to offer. RESULTS: Nearly half (494/1000, 49.4%) of the sampled "cancer cure" books for sale on Amazon.com appeared to contain misleading cancer treatment and cure information. Overall, 17 (51.5%) out of 33 Amazon.com results pages had 50% or more of the books coded as misleading. The first search result page had the highest percentage of misleading books (23/33, 69.7%). Misleading books (n=494) contained eight themes: (1) claims of efficacious cancer cure strategies (n=451, 91.3%), (2) oversimplifying cancer and cancer treatment (n=194, 39.3%), (3) falsely justifying ineffective treatments as science based (n=189, 38.3%), (4) discrediting conventional cancer treatments (n=169, 34.2%), (5) finding the true cause of cancer (n=133, 26.9%), (6) homogenizing cancer (n=132, 26.7%), (7) discovery of new cancer treatments (n=119, 24.1%), and (8) cancer cure suppression (n=82, 16.6%). CONCLUSIONS: The results demonstrate that misleading cancer cure books are for sale, visible, and prevalent on Amazon.com, with prominence in initial search hits. These misleading books for sale on Amazon can be conceived of as forming part of a wider, cross-platform, web-based information environment in which misleading cancer cures are often given prominence. Our results suggest that greater enforcement is needed from Amazon and that cancer-focused organizations should engage in preemptive misinformation debunking.