The description of the key '/tikz/graphs/put node text on incoming edges
' on p. 280 says:
The command
target edge node={node[]<options>]{\tikzgraphnodetext}}
is executed.
I think there's a redundant closing bracket there. It should be
target edge node={node[<options>]{\tikzgraphnodetext}}
Good catch. This is fixed now. Thank you for reporting.