Almost 1,000 ferns are documented and illustrated in typical Timber Press fashion, the 700 stunning photos and detailed descriptions will have you clambering to find suppliers for many of these ferns. There is a bias towards the United States in terms of some of the ferns and descriptions, however the vast majority of plants that caught my attention are readily available in the UK from a number of specialist suppliers.
Published in 2007, the Encyclopedia is now a good 5 years old, however I don't think this should be an issue, many of the newer introductions mentioned have been available for a while now, and many of the well known species are described with lots of cultivation experience of the author as well as numerous other enthusiasts. Olsen is an experienced plants woman and author and has plenty of experience behind her, having studied grown and photographed ferns for 4 decades. Foliage Gardens, her nursery has introduced many ferns into horticulture. Olsen is also a founding member and the first president of the American Hardy Fern Foundation as well as being the editor of the Hardy Fern Foundation Quarterly newsletter
Each genus is described in detail with a focus on the garden worthiness of each plant, providing detailed habitat and cultural requirements. Propagation techniques are explored in some detail, having never attempted to grow fern from spore I do fancy giving this a try, perhaps later this year I will use Olsens techniques and attempt to prop my own ferns! The book focusses on ferns suitable for the more temperate climates, however a number of stunning exotic species are also featured in the book.
Not quite an A to Z, the detailed plant directory starts with the genus Acrostichum and extends to Woodwardia (one can't complain I couldn't think of any fern genus starting with a Z either - if you have any suggestions please include them in the replies).
The books includes chapters covering the cultivation, history and fern structures leading to a number of lists of plants suitable for growing in a number of different conditions and habitats.
I would go as far as suggesting that this is the definitive such work on ferns and should be included in any good collection of horticultural texts.
The Encyclopedia of Garden Ferns is published by Timber Press and is available from all the usual book sellers.