In the final year of my Masters I took a course on the Ancient Novel, and as fun as it was, I now realise how heavily it was based on Holzberg, which is a great compliment to the book - I suppose it forms the basis of all modern introductory courses on the topic.
It's 129 pages, all in - including the author's note, bibliography and index, which is made up of five chunks: the genre; the rise of the genre; the idealistic novel in early Imperial times; the comic-realistic novel and finally the idealistic novel in the age of the second sophistic. A chronological route, then.
The opening two sections set the tone - the first, especially, puts down the thrust of the whole work - that the ancient novel exists as a separate and defined genre, which the second supports by describing it's origins. Both of these are convincing. Holzberg discusses how the novels we have exhibit clearly defined motifs (or inversions of these motifs) throughout, and how the form of the novels, while influenced by other genres, clearly came about from a conscious decision to create a new genre that was separate, unique and different.
Holzberg then goes on to discuss the various novels we have in chronological order, with a large focus on detailing their respective plot lines. This is of the highest importance because by the end of the book one has the overwhelming feeling that the novel exists as a separate and distinct genre, which exhibits clear and unique motifs throughout.
The text, as a whole, is an attempt to justify the study of the novel as a distinct genre and prove not only to posterity but to classical scholars that it's worthy of consideration and that it most certainly exists as single genre with defined parameters. Holzberg is successful in doing this, for sure.
The novel has perhaps been ignored as a genre until modern times, and derided by scholars as insignificant in the classical corpus - wispy sort of stuff not really worth studying. Holzberg organises a defence of it, and it works. I like the ancient novels - they're interesting, fun, escapist but with plenty of depth and worth.
There is nothing essentially wrong with the text at all - it's a fantastic introduction, and therein is perhaps the only qualm I have with it - it does nothing more than establish the novel as a genre, further discussion is not all that frequent. Introductory texts don't usually have to defend the genre they will discuss (too much, anyway) but the novel very much needed the help, and so I can hardy moan about the book being too "introductiony".
Having a more clearly defined conclusion may have helped, and given the reader a chance to have everything summed up, but it was perhaps Holzberg's active decision to not include one, and leave the work very much as a departure point - the very foundations, so to speak, upon which a study of the genre could be built upon. In that respect, it's not such a big loss.
I recommend the book for anyone who hasn't really considered the ancient novel before - it gives a nice overview of the genre and is easy enough to read. It's concise and to the point and should be the starting point for pretty much anyone interested in the novel, but unsure how to approach it or how it fits in with classical studies more generally.