It is available here . The book is organized like the Who's Who volumes, and visitors can choose to view text or PDF versions (heavy files: 1905 is 68 MB).
These volumes may have very valuable information for your Chicago ancestors. Details may be very detailed or sparse (it depended on what information the person named decided to supply). Information may contain names of spouse and children, birth dates, education, employment history, home/office addresses and other details. Some entries are much more detailed than others.
From the 1911 edition:
It is known that 841 persons whose names appeared in the previous edition have died and that 408 have removed from the city; consequently their sketches have been dropped, and 729 have been omitted for other reasons. The names, however, have been included in the present edition and reference has been made to the volume in which the sketches may be found.