Just for what it's worth, recently I posted a few observations regarding the pictures in that book, and for the sake of clarification, here was my cursory list:
More miscaptioned/unclearly captioned pictures in Titanic and Her Sisters Book:
Page 59 - illustration of the aft grand staircase
Page 113 - this is actually Britannic after launch
Page 118 - identified as Titanic; however, bow clearly says Olympic
Page 122 - lower left - this is actually Britannic's stern.
Page125 - this is Olympic, not Titanic
Page 134-135 - this is Olympic, not Titanic
Pages 142-143 - top is Britannic, bottom Titanic. Britannic was launched with an enclosed A-deck promenade, while Titanic's was launched with an open one. The enclosed portion was added in March 1912 before she sailed. The captioner apparently saw enclosed promenade and said, "Oh, this is Titanic then."
*most of the outfitting pictures in this book are of Olympic or Britannic, and do a good job illustrating how the Olympic-class vessel was constructed. However, I am only addressing the picture captions which mis-label those as being from Titanic.
Page 155 - these are of Olympic's GSC, 154 being D-deck forward, 155 being A/B deck aft.
Page 157 - Olympic's compass platform
Page 160 - Olympic's gym
Page 161 - top - Olympic's gym; bottom, indeed Titanic's gym.
The other confusing aspect of this book is that it compares olympic pre-refit pictures against post refit plans
Page 181 shows a furnished cabin similar to the unfurnished picture seen in page 173 that misidentifies it as a passageway.
Page 218 - this is not an Olympic-class dome
Page 246 - Titanic, although taken off the Isle of Wight, not Belfast
Page 251 - not J.J. Astor, but rather his cousin. The Astors boarded in Cherbourg. This picture was taken in Waterloo Station, London.
Page 298 - indeed this is Olympic's reading/writing room, BUT....
Page 307 this is identified as Titanic's reading room - note the same bump in the rug
Page 303 - I believe this "Captain Smith" figure could be actually Archie Butt walking aft. He was photographed earlier on the port side forward, wearing a long coat and cap. Captain Smith was gray haired, and this figure has dark hair.
Page 321 - These are Olympic's lifeboats. Titanic's never had white gunwales, while Olympic did in her first year of service.
Page 418-419 - this is not Britannic. I've heard it correctly IDed before, but it escapes memory - is it the Aquitania?
In the fitting out photos, it's sometimes easy to see which ship's parts are being photographed. Olympic's number was 400, Titanic's 401, and Britannic's 433.