Some may know that our former co-Moderator, Antonio Pereda (Old Kappa) was directly involved with the Baur Collection - I forget his exact title, he may have been on the Board of Directors or Trustees. Antonio had access to some of the notes and other literature concerning this storied collection - he shared one notecard with me and I got permission to include it in one of my INSJ articles, I think the one on Anraku(sai) if memory serves me.
The Baur book ("The Baur Collection") is a very large, comprehensive and expensive treatise which all serious students of this field should consider adding to their libraries.
US Amazon has it currently for $950, used:
But, if you shop it around and put in a Google following instruction, you can find a deal occasionally - watch for auctions which include libraries, which may include this book.
Also, caution, there are other Baur Collection books concerning Baur's collection of other Japanese and Chinese art in addition to netsuke - there are Baur books on Chinese Ceramics, and on Japanese Sword Fittings, among others - Google Search "Baur Collection" to see the breadth of this collector's reach.
Last, but not least, if you are interested in learning about the man who lends his name to these collections, Alfred Baur, a man (he died when I was one year old, after living a very full life) whose extraordinary generosity made all this knowledge available to future generations, see this:
"Alfred Baur brought together a collection of  objects which stands out as one of the most beautiful private collections in Europe today. A private collection reflects the preferences of an amateur and, as such, reveals the spirit of his time. Baur chose to buy "small quantities of rare works of art rather than large numbers of articles of inferior quality". Through his collections, he appears as a man of taste. During his lifetime, he donated his collections to a foundation which bears his name and that of his wife, a Genevese by birth: the 'Fondation Alfred et Eugénie Baur-Duret'"