In Paratexts: Thresholds of Interpretation, Jane E. Lewin offers an intelligent and energetic translation of Gérard Genette's Seuils (Paris: Seuil, 1987)—a study of "the liminal devices... that mediate the relations between the text and reader" (xi). Lewin's translation—her fourth of a book-length work of Genette's—is impressive in its stylistic and tonal faithfulness to Genette's erudite and playful French. Throughout Lewin demonstrates a clear understanding of the philosophical, historical, and literary interests that fuel Genette's thinking.  In the foreword to the volume, Richard Macksey situates both Lewin's present translation alongside her previous efforts, and contextualises the position Paratexts occupies in the corpus of Genette's criticism.
Paratexts has its origins in Genette's introduction à l'architexte (Paris: Seuil, 1979), and in Palimpsestes: La littérature au second degré (Paris: Seuil, 1982) where Genette develops the term "paratext" in his formulation of "five types of transtextual relationships":
The second type is the generally less explicit and more distant relationship that binds the text properly speaking, taken within the totality of the literary work, to what can be called its paratext: a title, a subtitle, intertitles; prefaces, postfaces, notices, forewords, etc.; marginal, infrapaginal, terminal notes; epigraphs; illustrations; blurbs, book covers, dust jackets, and many other kinds of secondary signals. 
In the introduction to Paratexts, Genette offers a similar definition:
A literary work consists, entirely or essentially, of a text, defined (very minimally) as a more or less long sequence of verbal statements that are more or less endowed with significance. But this text is rarely presented in an unadorned state, unreinforced and unaccompanied by a certain number of verbal and other productions, such as an author's name, a title, a preface, illustrations… These accompanying productions, which vary in extent and appearance, constitute what I have called elsewhere the work's paratext….Paratexts 1
While Paratexts is a hand list of the above (and other) terms catalogued in Palimpsests, Genette intends "paratext" to communicate the ambiguity of the prefix "para." Drawing on J. Hillis Miller's "The Critic as Host," Genette writes of the polysemy of "para":
'Para' is a double antithetical prefix signifying at once proximity and distance, similarity and difference, interiority and exteriority... something simultaneously this side of a boundary line, threshold, or margin, and also beyond it, equivalent in status and also secondary or subsidiary, submissive, as of guest to host, slave to master. A thing in 'para,' moreover, is not only simultaneously on both sides of the boundary line between inside and outside. It is also the boundary itself, the screen which is a permeable membrane connecting inside and outside.Paratexts 1n2
Although there is an intertwined and uncertain spatial and temporal order of a "para" object, the occurrence of a paratextual element is part of the publicisation of the literary work:
We do not always know whether these productions are to be regarded as belonging to the text, in any case they surround it, precisely in order to present it, in the usual sense of this verb but also in the strongest sense: to make present, to ensure the text's presence in the world, its 'reception' and consumption in the form (nowadays, at least) of a book.1
Genette is interested in the relationship between books and readers—and, at times, in how other discourses by authors and publishers stand between books and readers. This, however, is a tricky terrain to map. And if there is a difficulty in following Genette's conception of the paratextual, it is located in this cartographically blurry critical space (or, "threshold") which, for Genette, has no fixed location. (That is, not all books contain the same paratextual elements identically arranged.) To convey the core elements of this relationship, Genette formulates a simple algorithm that governs the whole of Paratexts:
The peritext includes elements "inside" the confines of a bound volume—everything between and on the covers, as it were. The epitext, then, denotes elements "outside" the bound volume—public or private elements such as interviews, reviews, correspondence, diaries etc.—although Genette does comment that "in principle, every context serves as a paratext." (8)
There is a methodological playfulness to Genette's paradigm of the paratext as he employs an approach that is at once aesthetic, narratological, and bibliographical. Unpacking the paratextual dynamics of "the cover and its appendages," for example, Genette distinguishes four book covers: front cover, inside front cover, back cover, and inside back cover (23-32). (Genette also explores the function of the spine of the book and dust jacket in this section—paratexts that contain several of the same elements found on the covers.) Combined the covers contain a variety of paratextual contexts that may potentially steer readers to have expectations of, if not to particular readings of the literary work. The name of the author, publisher, title, laudatory comments, excerpts from reviews, biographical notices, indication of genre ("a novel") and publisher information pre-dispose readers to opinions of the literary work before they have commenced reading the work. This seems straight forward enough. But a device as seemingly innocuous as a book's ISBN: number also influences readers interaction with the literary work. The numerical code indicates the language of the book, and the publisher, for example. Yet the presence of the ISBN: itself dates the book to after 1975—when the ISBN: system was introduced. The ISBN, then, hints at potential global associations with the history of a specific national literature, as well as local associations with an individual publisher and the genre(s) that readers have become accustomed to from certain press houses.
A book about the "liminal devices... that mediate the relations between the text and reader," Paratexts itself occupies a curious liminal space in the history of literary scholarship. It opens up and explores the critical terrain that exists between literary theory, and textual and bibliographical criticism. Here it stands as a welcome, provocative, and articulate theorization of the relationship between the features of the publication-publicisation process that can be found in a literary work and the influence that these features can have upon readers.
Lewin's translations of Genette's work include: Figures III (Paris: Editions du Seuil, 1972) as Narrative Discourse: An Essay in Method (Ithaca: Cornell University Press, 1980); Introduction à l'architexte (Paris: Editions du Seuil, 1976) as The Architext: An Introduction (Berkeley and Los Angeles: University of California Press, 1992); and, Nouveau discours du récit (Paris: Editions du Seuil, 1983) as Narrative Discourse Revisited (Ithaca: Cornell University Press, 1988).
Palimpsests: Literature in the Second Degree, trans. Channa Newman and Claude Doubinsky (Lincoln: University of Nebraska, 1997) pp. 1, 3.