This work is not a popular book addressed to the masses who can't read a Greek work or are not interested in academic books. It has no general introduction to the NT background, literary criticism, etc. (German theology students normally first study, besides languages, some books on the NT background and also some on exegesis such as the classic Conzelamnn and Lindemann's Arbeitsbuch zum Neuen Testament or more recent books such as Schnelle's Einführung in die neutestamentliche Exegese or Roloff & Müller's Neues Testament). Schnelle's present book does have an introductory chapter, but it deals critically with the previous German and English books on the same subject (French books such as Daniel Marguerat's Introduction au Nouveau Testament are omitted).
Most chapters of this book deal with one book/epistle of the NT. Each chapter has the same, very well organised structure. The major theories and arguments are discussed, everything is well exposed. Greek words are written with Greek font, making them a pleasure to read, and likewise for the few Hebrew words. The exposition is excellent.
This book surpasses any other book I have read by its clarity, readability and balance. It is really a scientific work. It is required reading for any student of theology in Germany (even including German fundamentalist evangelical seminaries, although these may better served than their American counterparts with Erich Mauerhofer's Einleitung in die Schriften des NT).
I have actually read it in the German original (4th revised edition, 2002). Unfortunately the English translation is based on an older edition. Masterful books like Schnelle's show that Germans are still the best at Christian theology and that anyone seriously interested has to learn German to read such books...
For those who want to go further, there is a book I like very much on the making of the canon, Lee McDonald's The Formation of Christian Biblical Canon (2nd rev. ed. ) and is going to be superseded by the author's new book : The Biblical Canon: its Origin, Transmission, and Authority (scheduled for Nov. 2006).