Amazing experience, gorgeous trails! Highly recommend to visit but maybe not during the summer or early fall months because it can be really really hot. Also, highly recommend to start the day as early as possible if you want to get a parking spot at the visitors center. The spots get completely full after ~7.30am. The shuttle is very convenient, no reservations needed. Only need a reservation if you are trying to do Angels landing.
It is difficult to describe the natural beauty of Zion National Park in words or pictures. There are so many scenic points all over the park. Some of my favourites were Lower Emerald and Higher Emerald pool. There is almost a couple of hours of hike from the base camp. It is a big park to cover in one day but you can take the bus from the base camp to quickly visit most important scenic points around the park. I visited the park in June, it was around 80F. There was lots of water in the river passing through the park. You should enjoy the beautiful sounds of the running water :) I planned my trip by staying the night in St. George, UT which is one hour drive from the park. I left the hotel at 7:00 AM and reached the park around 8:00 AM via UT-9. It is good not to drive in the evening or night because you can cover scenic UT-9 in the morning. My next destination was Grand Canyon National Park, so I left the park around 3:00 PM so that I could reach Flagstaff, AZ before the night. Doing this, I covered UT-9 all during the day time. UT-9 is a very beautiful scenic drive which you should not miss. Do have the following with you, - Sun block - Sun glasses - Stick for hiking - Lots of water