An Essay Towards an Improved Register of Deeds, City and County of New York, to December 31, 1799, Inclusive by Charles Fredric Grim, 1832, is available online at Google Books.
The book is simply an index to the deeds of New York County prior to the year 1800. In actuality there are two indexes, one for Grantors, the second for Grantees. The index for Grantors begins on page 2. The index for Grantees begins on page 169.
Having this book available online eliminates the time consuming need to consult the indexes for New York County Deeds that were filmed by, and are available through the Family History Library, at least for years prior to 1800.