Owners of Lancaster's original Active Filter Cookbook: read on. I just bought Lancaster's Active Filter Cookbook, Second Edition. For years I have owned a copy of the original (1975) edition (mine is the 17th (1992) SAMS reprinting). Based on a cursory inspection, I can find no difference between the 1992 reprinting of the original edition and the so-called second edition. The Preface, the Table of Contents, the page numbering, the contents of numerous pages I examined, the List of References, the Index, are all identical, as far as I can tell. There is no new preface to the second edition. There is no description, either inside or on the outside cover, of what has been changed in the second edition. Based on my examination, I would recommend that, if you already own a copy of the first edition, there is no reason to buy the second.