As much as I liked Amiblitz, Id recommend using the Ultimate Blitz CD if youre using a more modest "real" Amiga. It contains Blitz 2.1 and a shedload of updates, plus lots of good examples. In regards to the manual the page recommended in this thread (
http://amiga-manuals.npage.de/index.html) has good copies of everything in PDF scans (manual, reference guide, user guide, etc.). Bare in mind though that it's spread between both applications and ebooks. An AmigaGuide version of the manual itself is also included on the Ultimate Blitz CD (which is quite easy to find (Back To The Roots has it for example)).
Blitz itself also has good "intergrated" help. Pressing help will give you the syntax for any command that the cursor is currently occupying in the editor for example.