Wolfram George Schmid takes hostas to a very serious degree in his book "The Genus Hosta." NJBob provides a link to books recommended by the American Hosta Society and Mr. Schmid's book is one of those listed. Their review summarizes the book quite well:
"The Genus HOSTA, W. George Schmid,1991, hardbound
Timber Press, 133 S. W. Second Avenue, Portland, OR 97204, USA
A truly comprehensive scientific and horticultural study of the genus hosta. The largest part of the book is devoted to detailed descriptions of all species, varieties, forms, and registered/non-registered cultivars. Professional horticulturists and hosts enthusiasts will appreciate this first-ever comprehensive classification system listing approximately 3500 names and synonyms including 300 Japanese names printed in kana. Also included is information on care and cultivation, propagation and hybridization, landscape uses, and pests and diseases. This book is a definite reference work."