If you can work out index.html's full pathname, it may be possible to open from Chrome or any other browser.
For example, file:///home/dave/devel/webserver/index.html
Note the URL starts file:// and is followed by the complete name.
The URL directs the browser to : the local file index.html, which is in the folder 'webserver', which is in the folder 'devel'; which is in the folder 'dave'; which is in the folder 'home'.
The book's Android pathname will follow the same convention, but the folder names above 'inc' will be different.
I think the problem is Android. It's organised and customised to suit Smart Phones, and I don't understand it well enough to give clear instructions. index.html should just work, but Android has a bunch of security and other differences that might make the book fiddly to open.
You might try eBoox, an Android e-reader that lists zip as an input. It may be able to open and read from the zip download directly, or allow the Android to be searched for index.html
If no-one can explain how to tweak Android, the simple answer is to read the book on a Windows, Linux, or Mac computer or an e-reader.
Dave