This would be quite good if you're a stranger to the whole area (I'm not a cyclist though, I bought it for the pub walks). For what it is, it's good enough, giving ratings for the walks in terms of difficulty, helpful info on the pubs, and it gives a good variety in terms of length, type and terrain.
The info it gives is good, but it covers really only the obvious options though, (East Prawle and the like), and because of the variety included, 40 options is no way enough.
There may be a certain cross-over in the market, between pub walkers and cyclists, but I'm not one of them, (frankly, cyclists muck up the land for the walkers and cause soil erosion to boot). I'd prefer a book that was either one thing or the other. Also, because it covers such a large geographical area, you'll have to be nipping about all over the shop to get your money's worth from this book. For whichever particular bit of Devon & Cornwall you're interested in, the odds are you'll be lucky to find three or four options you can do in this book. That's why I took mine back to the shop.