As of early 2014, softback and hardback editions up to and including 1946 have been published.
From the 33rd (1896) edition onwards hardback copies became available at twice the price of the softback.
Collected volumes have also been produced as both hardback and softback books.
A less expensive binding method is that used for paperback books (sometimes called softback or softcover).
Approximately 150 softback copies were produced of each year from 1864 to 1878 and made available either as part of a set or as singles.
The original publications were in an unusual format (15 cm x 7 cm softback pictorial).
The run was limited again to 150 softback sets.
The series is printed by photo-offset in softback format but to very high quality.
