Are these files legitimate? I've downloaded three of them today.
I extracted each zip file. Then I extracted the resulting zip file. Then
I encountered an exe file for ebooks. I launched the exe files
within a sandbox. Each file immediately wanted to contact the internet
but of course could not because of my Sandbox and, for further
security, my firewall settings.

So why do contributors make the ebook so complicated to download.
I see other contributors of zipped ebooks give you the ebook
without any mulitiple unzippings and exe files.

Is this simply people trying to infect Mobilism users' computers?

[merry60]

Are these files legitimate?

The files you download from posters are legitimate. The exes you download from filehosts are not, and should be avoided. Please read this topic, it will help you navigate filehosts: Subject: .exe or Virus warning after downloading an app, ebook etc.