Slightly Foxed Bookshop on Gloucester Road) because it's one of the more comprehensive I've found.
The book starts with some brief chapters on herbs in general, then each individual herb is described under several headings: Virtues, Description (or Appearance), Growing, Harvesting and Uses. Several headings are self-explanatory; Virtues covers folklore, medicinal properties and other interesting facts, while Uses gives directions on the preparation of simples (medicinal and cosmetic) and, in the case of the kitchen herbs, a recipe, or other comments on its culinary uses.
There are two useful charts at the back, on growing and usage. There are a couple of inclusions which might be slightly unexpected - for instance, rose hips, which were much used as a source of Vitamin C during WW2* - and the range considered is wider than the usual kitchen-garden list: there are some plants here which we'd normally consider to be wildflowers or weeds. If you wanted to create a herb-garden like those of earlier centuries this, in conjunction with one of the early Herbals, like Mrs Grieve's, would be an excellent and practical reference work.
* As a child in the early 1960s, our school took part in a national scheme to collect rosehips - we would go out every evening with bags and, at the end of the week, the total would be weighed. There were lots of wild roses growing around the small Scottish torn where I grew up and we collected huge quantities which were sent off to be made into delicious rosehip syrup. I think the practice had stopped by the time I left primary school.