It spends far too long stating what might be wrong with GPS (but which is almost never the case).
As to practically using it for planning a route, monitoring airborne wind, time enroute and to go, picking sensible waypoints, using the internal databases, real route planning, i.e producing a PLOG from your planned route - almost nothing. Nothing about obvious 'sense checks' you can make to ensure your routing is correct and the thing is actually working.
And the user waypoints might be wrong!!!
