Most people know that Marie of Romania was born a British princess and was the eldest daughter of Prince Alfred of the United Kingdom and Grand Duchess Maria of Russia. She married the future King Ferdinand of Romania in 1893, and she ruled as consort with the title Queen of Romania for almost 13 years (1914-1927). She also wrote and published books on royalty and Romania.
She wrote many books to bring Romania some "exposure" to others; most people had heard of Transylvania, or of Romania, but they really didn't know much about this land. Marie also knew that the area needed money, and the means by which she contributed to increasing the kingdom's income was to write about herself and about Romania. One of her more famous books, The Story of My Life, is still available, but because she was a part of the "war to end all wars," other writers have written about her. This is the means that Bran Castle became a part of the royal residences, and why Marie spent time in Transylvania, so that there would be exposure to a royal person, which would allow for more money, as even during that time, royalty is money.
She wrote books to give herself a creative outlet, and she also understood that there was a need to promote Romania to America, where she knew that there would be money, or funds, sent to Romania after the end of World War One. This, she took to mean that there would be needed quickly as Romania, after the Paris Peace talks, had grown in population and territory. Many of her books were published between 1912 and 1933, but most were written or published during the war or after.
Just like Bran Castle provides a lot of money to Transylvania and Romania, Queen Marie understood that she needed to make money for Romania to keep her people happy and content. She simply had to look to Hungary and Austria to understand the importance of this fact.