Learned something new as I checked something before answering your post ---- Contrary to what I had always heard about Isaac Watson Dunham, he did NOT die before his book, The Dunham Genealogy, was printed in 1907.
He died 30 December 1915. According to an obit, he had failing eyesight for some time so he was living with a daughter. His bio info can be found on page 109 of the book which is digitized -- see internet archive or google.
BUT BEWARE ----- USE CAUTION ------ DO YOUR RESEARCH IN ORIGINAL RECORDS !!!!
Isaac's book is full of errors AND the ancestry given in the book for Deacon John Dunham is FICTITIOUS/NOT REAL. There is also now better information on his two wives. (Abigail's maiden name was not Wood.)
You would be better off checking out The Dunham-Singletary Association. http://www.dunham-singletary.org/mw/index.php/Main_Page