Whether a title-entry is needed is open to doubt, but as the title of the book is enigmatical it is safer to give one. The rule for all title-entries is to give them under the first word not an article, and it would accordingly be
In darkest England. Booth, W. [1890]
but the probability is that nine men out of ten would remember the book as “Darkest England,” and look for it under “Darkest,” and therefore it might be more useful if the entry were
Darkest England, In. Booth, W. [1890]
83.—The subject of the book requires that it be entered under whatever heading may be adopted for the social question, say
Poor and poor relief.
Booth, W. In darkest England. [1890]
No entry is called for under “England,” unless everything relating directly or indirectly to the home-country is to be brought together under that heading or “Great Britain.” If this is so, and it is to be faithfully and literally carried out, it will become so large as to need very elaborate sub-division, and even then, in the catalogue of a British library at anyrate, its extent will make it of little practical value. In large catalogues page after page would be filled to no great advantage, and therefore the best course to adopt is to make the entry under the exact subject, as shown, ignoring “England” if the book deals with the country generally and not a particular corner of it. By this plan a book upon the “Poor of Essex” would be entered both under “Essex” and “Poor,” but books like
Ruskin. The art of England.