Advantages of Serial Publication of this Reference Work
First, publication in a cumulative series enables ongoing updating of each title record. Especially in the case of periodicals, where often several libraries must be visited before a complete run can be identified, this updating is likely to carry on for some time. And as other scholars complete work over the life of this project, the benefits of their research can be incorporated in this Directory.
Second, series publication in which each new series replaces the previous enables both the updating of previous title records and the interspersing of new title records throughout the alphabetical listing. In other words each new series provides an entire A-Z alphabetical listing until the total of 125,000 records is achieved. Although online format is more suitable for production and distribution and use of the Directory than is the printed volume format, even the inevitable waste of 100 outdated volumes (Series 1  + Series 2  + Series 3  + Series 4  = 100) in order to arrive at the final fifty volumes of printed works is a minimal price to pay for the great advantages of series publication. As powerful as the online search engine is, printed books have an impact which the more elusive electronic format can not hope to reproduce. Moreover, books are less susceptible to technological obsolescence.
Third, series publication puts early results of a very large project into the hands of readers who might wish to suggest emendations and changes of various sorts for later parts of the series. Should the project be interrupted, at least some of the editor's work will have been made available to scholars interested in nineteenth century England.
Fourth, libraries are able to purchase so inevitably expensive a research tool in relatively small increments. Those who purchase the first series and wish also the second, can purchase the enlarged second for only the incremental price. On the other hand, those who do not purchase the first, must pay the cost of both first and second when purchasing the second, and so on.
Fifth, as the research for this reference tool proceeds not only by subject but also by geographical region, it is convenient to cover one more region as well as one more set of subjects in each of the series. Although London is the place of publication for the majority of nineteenth century newspapers and periodicals, and for that reason is the research center for each of the series, yet many titles can be found in only one library in a remote part of the country. Every geographical region of the country must be covered because virtually every library contains a number of uniquely- held titles, as well as assorted issues of well-known titles for which no library holds a complete run.
Inexpensive to buy, difficult for librarians to catalogue and store, and notoriously current (so supposedly more quickly outdated than books), newspapers and periodicals have often been treated as ephemeral by historians and curators as well as bibliographers. Until now we have had much less access to them than to books.
Now The Waterloo Directory Series provides much greater access to them than scholars currently have to the titles listed in Peddie's English Catalogue of Books: access by means of customized electronic search routines providing groupings of titles by date or people or place or subject or issuing body, access by way of photofacsimile title pages, access by any combination of the 26 fields of data per title, access by bibliographical description of each title, including library holdings. In other words, this reference work, at least by the completion of the five-series, fifty-volume set, will provide a more powerful and detailed bibliographical tool than is yet available for printed books.