When we visited this Park it was white Sand National Monument. But now it is national park. Remote gypsum place in New Mexico.
It does not have too many hikes but even short hike is tough because of sand. Patterns on dunes made by wind are great.
You can do all trails in one day and spend some time to try sledding on these dunes. You can buy sled in Visitor Center and even return later and get some money back. We gave to family on the way from park.
Try the longest hike Alkali Flat Trail – 5 miles round trip – for sunset or sunrise. This time is beautiful for light. You can find here lot of soaptree yucca and other plants. We were there in winter and weather was just perfect. During summer is hot and make sure you have enough water.