Complex sentence: The first edition of the book was published, without Kant or Fichte's knowledge, without Fichte's name and signed preface; it was thus mistakenly thought to be a new work by Kant himself.
Split into simpler sentences: The first edition of the book was published without Kant or Fichte's knowledge moreover without Fichte's name or signed preface. It was thus mistakenly thought to be a new work by Kant himself.