On the face of it it’s really a bit odd to start our books off with a page which adds nothing to the package.  After all, you know the title by the time you reach this page.  And just by turning the page you are able to reach a much fuller version of the same thing.  Why do we persist in adding a half-title?

The origin of the half-title, insofar as we can really know these things, goes back to the earliest days of book manufacturing: printed books would be stored as folded sheets until they were bought by customers, who would then arrange for hand binding on their own account.  If the first page in the stored book block was the title page, there was a risk of its getting dirty or even torn.  So the idea developed of protecting it by an additional leaf.  In order to identify what followed, the practice grew up of writing the title on the outside, and from there it was a small step for some bright spark to come up with a page carrying a typeset ID.  We are all bound by conventions we none of us suspect, so a book without a half-title just looks wrong to us.

The oddness is compounded by the growing habit of including a second half-title at the end of the front matter (which is usually called “prelims” in Britain).  We started doing this in order to beef out a book to fill an even working, but it now seems to have become a standard item in the make up of books from some publishers.  With sheetfed printing of short run books, even workings were more significant, and we developed a number of techniques to avoid blanks.  We used even to resort to the last-minute addition of Part title pages which were not included in the pagination.  But the extra half-title at the end of the front matter was always a nice two pages you could gain without effort.  Publishers for some extraordinary reason seem to regard blanks at the back of a book as an affront.  I’ve never met the reader who said “I’m not buying this book because it has too many blank pages at the back”, but maybe I’ve led a sheltered life.  I was always happy enough with blanks:  in my time I’ve added four blanks at the front and ten at the back of a book without batting an eyelid — well, maybe just batting it once or twice.

Originally the half-title was called the “bastard title”.  This is just the word used in the sense of inferior, or debased origin.