Detail and details can be both countable and uncountable, though not necessarily at the same time. Countable: Here are all the details on price, games and extras. Countable: This enabled them to remember every detail of the story. Uncountable: He invariably remembers everything in great detail.
Usually, I send to a client "Cover Letter" with phrase "May I get the details?", if I need to get more information about his project. Suddenly, I have discovered that it is not very polite. And now...