The BlitzBasic Full Foundation Tutorial guides you through the Blitz language without the use of difficult terms or concepts in a very straight-forward approach.

One way is reading it online, right here.
But you can also download it, then read it and play around with it directly from within Blitz.
Ofcourse you could also just take a peek to know what you're downloading :)

Part 1 - Introduction To Variables
Part 2 - Single Basic Variables
Part 3 - Conditions
Part 4 - Loops
Part 5 - Variable Collections
Part 6 - Routines
Part 7 - Game On

The summary is actually a compact design of the entire tutorial for more experienced coders.
So if you understand all the basics of programming, the Summary is the right thing for you :o)
Explained are the ways in which Blitz works as well as the system commands and glances of the language reference.