Best things about this book are the page size (large), the typographic layout (stylish yet well-ordered) and that it is printed in full colour throughout, unlike cycling books by cash-strapped smaller publishers.
As mentioned, the text layout is well structured, with each climb having an introductory side-column of information listing the perceived relative difficulty, length, average gradients, etc, in addition to the main text that deals with the description and Tour history aspects.
However it was a fatal mistake by the publisher and/or author to not include proper maps and gradient profiles. There's a kind of whispy-looking doodle of a map for each climb, placed in the margins of the pages, but the twistiness of a route is less important to riders hauling their weight uphill than knowing more precisely how steep it is going to be at various points and where the changes of gradient pitch will occur. By omitting the potentially useful diagrams that are promised in the sales blurb (see the Product Description) the book has been relegated to the level of a mere coffee table book, rather than the useful reference tool that it could have been. It should have been both really.
I'll skip the copy-editing deficiencies, except to say that these are embarrassing evidence of insufficient time being allowed for proof-reading and corrections.
A lesser complaint is the quality of some of the photographs, which sometimes look over-exposed. In some cases the images look like they have been scanned from low budget prints. I know it can be difficult to photograph a scene in harsh bright summer sunlight on these mountains, where there are extremes of light and shade, but I wish a bit of time was spent doing some digital correction work to hide the technical defects. Generally, I think the layout of the photos nicely integrates them with the text, although the chapter opener spreads are a little bit bland compared to the other pages. Perhaps the openers could have been made more useful by also including, as another reviewer suggests, some kind of regional map marking the relative locations of the climbs included in the chapter.
There are a number of similar books to this one published in France. Most don't have such beautiful typography as Tour Climbs, but they all have more useful diagrammatic information. Of them, the book 'Grands cols - les montagnes du tour de France à velo' (by Nicolas Moreau-Delaquis) is the one closest in form to Sidwells' book, yet it also manages to include full page colour maps and gradient cross-sections as part of the package.
So, in other words, despite Tour Climbs' good points, the ultimate guide in English has yet to be produced. Hopefully, if Collins ever correct the text for a future edition they will also give us some locational maps and include an appendix section of gradient profiles - then we can all award it the 5 star reviews that a book like this ought to have.