I bought this simply to check out the Westgate Horror. I have cycled all the paths on this route, but not together as a loop, so am looking forward to trying that. And yes the hill it starts with is horrific, twice as difficult as the ridiculously overhyped Crawleyside. A word of advice regarding this route is don't take the authors advice to sneek through the old quarry works at the bottom of Sedling Vein. This is privately owned residential land with footpath access only. I wandered down there in error once and while the owners graciously let me pass through the quarry, they asked me to dismount and push the bike. And no, I couldn't find the bridleway halfway down the vein either...
The problem with this book is it's age (16 years at the time of this review) and it hasn't been updated. The Hamsterley routes are largely redundant since it became a fully fledged trail centre and the Consett to Sunderland route (or 'Sutherland', as the page headers state in error) hasn't existed in this form for years. You can follow the route in a fashion if you know the area, but much of the old C & S Railway Path marked on the map all the way to Sunderland was in fact reopened as the Metro railway years ago. The best route is to stay on the north of the river at Cox Green and follow the C2C cycle path.
Another impassable route is Durham to Finchale Priory. The route is possible in theory, but bikes are no longer allowed in the woodland/riverside within the Priory. That's already 2 out of 28 routes I know are no longer rideable and I haven't got up off my sofa yet.
I will be trying the Weardale routes as I know the area, but may scout some locations beforehand to be sure some supposed bridleways are definitely accessible, but given at least the Sunderland route is now non-existent it would make me wary about trying some of the other long routes in unfamiliar areas.
I appreciate the author put great work into this, but given it's effectively 16 years out of date I would suggest this book be used for ideas on the most part and routes are checked against tools we now have available, i.e. satellite imagery on Google Maps etc.