Over two decades have elapsed since the passing of R’ Yaakov Kamenetzky Zt”l. Although he has been the subject of two extensive biographies, surprisingly little has been written about his scholarly work. His work has not been the subject of any academic papers to the best of my knowledge, and more surprisingly, in the so called “yeshiva world”  his chiddushim are rarely studied and certainly not discussed and expounded on in any shiur.
The lions share of R’ Yaakov’s legacy is undoubtedly his chiddushei torah in the traditional sense and I hope to expand on these in a future post. A good illustration of R’ Yaakov’s methodology can be seein in the note of the publisher in the introduction “We had to omit some of R’ Yaakov’s chiddushim because they were found to be identical with that of Rishonim that had not yet been printed in his lifetime.” The relationship between his Emes L’Yaakov and the works of the Rishonim can be seen both in his writing style (R’ Yaakov wrote in a very clear concise writing style never adding in extra word – See the introduction to EY on SA) and his methodology. The older and newer (Brisker) pilpulistic style is almost entirely absent from his work and in its place we have the more direct approach in the style of the Tosafists, the Aruch LaNer and the Netziv.
R’ Yaakov was possessed of an extremely sound (albeit unscientific) critical sense. He paid special attention to the intention of the author in writing his book , to the particular writing style of the author , and a very careful textual criticism 
His chiddushim focus on Gemara, Rif, Rosh and Rambam. He rarely cites the Talmud Yerushalmi or any of the later Achronim. Apropos of the name of the sefer, truth is the hallmark of all his writings. He avoids forced questions and fanciful, convoluted explanations. All of his answers are faithful to the text and its authors. To paraphrase the Seridei Eish, his work undoubtedly represents the historical Rambam and not simply his own Rambam .
For the moment I would like to focus on several of the more diverse, colorful elements
that R’ Yaakov makes use of in his Chiddushim. These include a knowledge of history, some fascinating amateur linguistic studies, knowledge of grammar and in interest in the origin of certain Minhagim
 See some interesting comments from R’ Yaakov on the modern Yeshivos here.
 He notes for instance that the Taz wrote his sefer originally on both the Tur and the Sulchan Aruch and for this reason some of the notes of the Taz are on the Tur and not on the SA (See Emet L’ Yaakov (henceforth EY) on SA – 66,7 and see the note there that corroborates this from the inscription on the Taz’s Tombstone). He also notes that the Rosh was originally written as a Pirush on the Rif (EY on Shas – I can’t reacall exactly where at this moment).
 He notes that the Posekim – specifically the Rambam, always phrased their Halachas in the manner of לא זו אף זו and in this manner he finds nuances in Halacha or in the Rambam’s interpretation of the sugya that would otherwise not be noted. (I myself have once made use of this כלל to good effect as I hope to demonstrate in a future post come Purim). He notes when the Rambam changes from the order of Shas or omits something that he should have cited. And in the same manner he analyses other seforim (in particular the Mishna Berurah for which he had great respect. See the introduction to EY SA and see my earlier post on one aspect of this.)
 This can be seen on almost every page. He carefully examines variants between the Rif’s text, the Rosh’s text and the Gemara, textual errors in the Rambam, conjoined Dibbur Ha’Maschils in Rashi , and the like. In this he is a worth successor to the Bach, Maharshal and the Gr”a He generally tries to back this up by speculating what might have caused the error. See for example EY Chullin 60b. In almost every case his emendation were validated by the new Oz' V' Hodor Talmud or the Frankel Rambam.
 Although R’ Neustadt has generally done an excellent job in producing his grandfather's (in-law really) seforim, in this he erred greatly. He ought to have placed the chiddushim on the Rambam in a separate volume so that they can easily accessible to those studying the Rambam. At the very least he ought to have included an index to the relevant material. As it is besides for several references in the Frankel Rambam his chiddushim are virtually inaccessible (and therefore unknown) to those studying the Rambam.