If you’re planning to visit Melk Abbey, be aware that Hotel Donauhof is not within walking distance—you’ll need to take a taxi, which costs about €16 each way. Alternatively, there's a bus that runs only once per hour.
The hotel provides no in-room amenities—not even, tea or bottled water—and there is no air conditioning, which can be uncomfortable in the warmer months after June. There are no activity area around the hotel, with no restaurants nearby except the hotel’s own. During our stay, the elevator was out of order, and we had to carry our suitcases up the stairs.
If you're visiting Melk Abbey, I would recommend staying in Melk itself. You'll find similar or lower prices, access to a charming small town, and several dining options within walking distance.