I use both in combo.
The Kettelwell book is good to keep a running log of the mileage, shows the surrounding areas of waterway (anchoring).
Skippy Bob gives good 'magenta line' info - hazards, anchoring holes, 'dog potty stops', etc. Skipper Bob also has a marina guide - prices, approach depths, etc.

Doziers Waterway Guide is good for choosing a Marina, etc. - is targeted towards stink-potters.