It sounds to me like the example code from the book doesn't work without alteration because Blitz2D defaults to using the FrontBuffer, whereas BlitzPlus defaults to using the BackBuffer. I can't be certain as I don't own BlitzPlus.
Try running the original example code in BlitzPlus, but add the line 'SetBuffer FrontBuffer()' directly after the Graphics command. Does it work then?
Try running the original example code in BlitzPlus, but add the line 'SetBuffer FrontBuffer()' directly after the Graphics command. Does it work then?