I'm reading a book, and I found a sentence where I don't understand the grammar. It seems as the writer wants to write a statement, but uses the structure of a question. The sentence is highlighted in the following paragraph:
In the first ten paragraphs, he touted his engineering skills, including his ability to design bridges, waterways, cannons, armored vehicles, and public buildings. Only in the eleventh paragraph, at the end, did he add that he was also an artist. "Likewise in painting, I can do everything possible," he wrote.
Isaacson, Walter. (2017) Leonardo da Vinci.
Shouldn't that sentence start with "he added" instead of "did he add" since it's not a question? If it's correct, is it something people usually use when they speak, or is it more like something you would find in books?