Robert Massie is useful as a starting point

Are Robert Massie's Dreadnought and Castles of Steel good naval-history books?

They are good introductions to the period, even if they are not the most exact or detailed academic works.

A book need not be the most complete academic treatment to be useful. Some works tell the story clearly enough to bring readers into the subject. Robert Massie's books fall into that category: strong introductions that may leave a slightly imperfect chronology or framing but still help readers begin the period.