Exactly. I asked preplexity.ai what it knew about the site's content. Here is what it said:
Downloads from modusdever.com are likely illegal. The hosted PDFs, such as Langford's Starting Photography (5th ed., 2007), The Hasselblad Manual (7th ed., 2018), and Ansel Adams' The Print, contain explicit copyright notices from publishers like Elsevier/Focal Press, prohibiting reproduction or distribution without permission.
Copyright Evidence
These books assert "All rights reserved" and require prior written consent for any sharing, including electronic means; the site offers them freely without such authorization. Wolfgang Tillmans exhibition catalogs also note rights managed by galleries and licensing agencies, not released for public download.
In my view, a better way to get this book is find a used copy on Amazon or Alibris.