It comprises a catalogue of running challenges (100 in total, split between England Scotland and Wales) varying in distance from 5km through to over 1400km (that one is Lands End to John O'Groats). Most are between 20 and 100 km. All runs are graded 1 to 4 according to navigational difficulty (1 is waymarked throughout, 4 is not waymarked, may comprise complex terrain and requires good self navigational skills).
Many of the longer, and harder challenges either are fell races, or individual challenges regarded as classics in the fell running community, which require some considerable training, recce-ing and organisation in order to complete it (eg The Bob Graham Round, Paddy Buckley Round and Charlie Ramsay Round). For the most part, website links are given so that interested parties can find out more detail (though there wasn't any given for the BGR, although one exists). In this way each challenge can be described succinctly, without clogging up the page with lots of detail.
Most of the events are definitely not for the fainthearted (or those who are not runners used to running off road and on mountains); would-be participants should consider not just the distance but the total climb given for each event. Approximate times are given to cover each route, which are calculated by the Jones Ross formula which is mentioned at the end but, sadly, not explained. There are magnificent photographs throughout, alongside or overleaf from every listing. My one grizzle is that I would have liked a caption for each, (on the longer ones especially) to say whereabouts on the route it was taken, or which mountain summit is featured.