Runk's is somewhat of an odd work, but useful in its oddness. It was published in two volumes, totalling around 1,400 pages. Volume 1, which is the one currently available for free through Google Books, starts off with an almost 80 page general history of the state, most focusing on the early period of settlement and colonization. After that, it goes on for about another 100 pages with brief biographies of some of the prominent men and families of the state. Following those begins the real meat of the work -- its "Biographical and Genealogical Sketches".
These sketches are short, anywhere from a few paragraphs to a page or two, pieces relating the biography and genealogy of prominent, but usually not particularly famous, Delawareans. The subjects are primarily well-known people in their communities and/or from well-known families, but not quite to the level where you'd find them in a conventional history book. As luck would have it, these are exactly the kinds of people who tend to show up on the Mill Creek Hundred History Blog. I end up using Runk's a lot, and it's usually one of the first places I check when researching an individual or a family.
The sketches themselves generally give a brief amount of information about the subject's life -- more of a blurb than a bio, really. However they usually include a lot of information about the subjects lineage and ancestors, making it a great resource when trying to trace the history of a particular family. The information is, for the most part, fairly reliable, but not foolproof. It seems that much like Scharf's book, this one was what we'd now call "crowd-sourced". The book's Preface describes it this way:
In other words, the sketches were solicited by Runk from the subjects themselves or their family members, then edited to fit a uniform format. As it turns out, not everyone in the 1890's had 100% accurate information about their families, but they're generally pretty good. The one major drawback the work has (at least in printed form) is that the sketches are in no particular order, and there is no index. To make it easier to use, Bill and Martha Reamy republished parts of the work, with a complete index, in 1998. This had been available online for a while, but was taken down last year (if I recall correctly).[T]he biographical and genealogical sketches of representative citizens now living, and those departed whose lives have conferred distinction upon their native places, were gathered from the most trustworthy sources by careful note-takers. After being arranged by competent writers, and neatly type-written, these biographical and genealogical sketches were submitted by mail and otherwise, for correction and revision, which we hope was so thorough that few if any errors in facts, names or dates will be found in the complete work. Those who furnished the data are, therefore, responsible for its genuineness and authenticity. Great care was taken to have the sketches as free from error as possible, but we do not hold ourselves responsible for mistakes, as no charge was made for the insertion of any reading matter contained in the book.
However, earlier this year the entire, original 1899 first volume was posted on Google Books in searchable form. I don't know if there are any plans to digitize Volume 2, but I really hope there are. In the meantime, Volume 1 gives us a lot of great information on subjects about whom little or nothing else is available. It's just another one of resources I use quite often, so thought I'd write it up. Hope it helps!