Another book that I forgot I had is Clive Jermy and Josephine Camus (1991) ‘The Illustrated Field Guide to Ferns and Allied Plants of the British Isles.
I find the format of this book clear and easy to follow because each fern species is given its own double page spread. For example for Asplenium trichomanes ssp quadrivalens which I looked at in a previous post there is a silhouette of a leaf blade on the left hand page with a brief list of key features with diagnostic ones highlighted in bold. there is also a drawing of the whole plant to give an idea of its habit. On the right hand page is a fine detailed line drawing of part of the pinna and rachis illustrating the outlines and shape of the veins and indusia. As well as the descriptions there is a brief description of the habitat and conservation status as well as comparisons with other similar species.
The drawings and the layout of this book are excellent.