Our group has been camping at Sly Park together and respectively since 1996, and we can't ever get enough. It's a very popular camping spot, so I recommend planning and reserving sometimes several months in advance. Weekends book up quickly, but weekday camping is easy to find.
They have several different campsite areas, and we typically frequent Pinecone Strip in the 30+ numbered sites. They have several water view sites, and many others deeper into the area. The lake is GORGEOUS and amazingly cool during the summer, and we also love winter camping in the snow as well. Sites have fire rings and picnic tables, and the reservation page has detailed descriptions of each site for you. Lots of hiking, biking, and equine camping which is so fun to see.
The stars are breathtaking at night. Gotta be my favorite part. It's also fun to look across the lake and see all of the campfires sparkling in the distance. That said, they also follow fire season safety and you should plan for that.
There's a little general store across the street from the entrance with essentials and camping basics, and loads of places nearby for firewood and more specific purchases.
Access to the lake is relatively easy, and they have a day use area separate from the camping areas.