Romance novels vary in how many words are in each book. Short romance novels typically average around 55 thousand words in one book. Most romance novels are usually short books with approximately 200 pages.
For the Harlequin novels the average is any where from fifty thousand to one hundred thousand. The amount of words in a novel is really up to the publisher and writer. Different genres have different requirements. Better known authors have more freedom than the rest.
It really depends upon the type of romance novel. The words in an average romance novel can range from 55,000 - 100,000. If you are writing an historical romance novel, which is usually a bit longer than your average run of the mill romance novel, the word count will be closer to 100,000. Harlequin Romance novels generally use the count of 250 words per page as an average number.