Have you not looked at the avast Help Center link in the avastUI, that accesses the avast help file which is quite comprehensive ?
Sorry but it may be more "comprehensive" than the "Getting Started Guide", but stills falls far short from being a substitute for a
good User Manual.
Download the pdf file - Avast! Free antivirus Quick Start Guide http://files.avast.com/files/documentation/quick-start-guide-free-en-ww.pdf
Appropriately named--as only provides just enough documentation for one to "Getting Started" on using the basics of avast!.
Case in point, there's not enough info provided avast! AIS features, AIS Getting Started, and the AIS Help
combined that provides any
real in depth detail documentation on using
all of the Firewall options/settings; or to make a one-to-one comparison of the AIS Firewall features/options with another firewall's features/options.