I didn't have a GitBook account and appears I'm unable to make one with the "legacy" version of the site when clicking on this link:
Download ebook for offline reading - [link](https://www.gitbook.com/book/learnbyexample/command-line-text-processing/details)
```
401
Unauthorized
New accounts should be created on the new version of GitBook. Head to https://www.gitbook.com
```
edit: able to download but wasn't able to preview or attempt to login on the legacy URL
I think I will change the download link to only the PDF version (https://legacy.gitbook.com/download/pdf/book/learnbyexample/command-line-text-processing) instead of the current link. That'd prevent the confusion you faced.
For preview, you can use the other link mentioned in README: https://learnbyexample.gitbooks.io/command-line-text-processing/content/