Books for reading and passing the time: there is a lot of down time.
Temperatures can be hot, cold, or just right. Daytimes usually warm but can go either way. Early mornings and evenings can be downright cold. If you are traveling in an open vehicle when it is cold, you will know it. I stocking cap and some gloves will be a life saver in addition to a light wind breaker over fleece. Various thickness of wool, cotton, or fleece during the day are very adjustable and let you tolerate a range of temps. Vests are very useful for this very purpose and can be any of the above materials and even a light very compressible down vest with plenty of comfort for little space or weight.
Cushion, journal, camera. Realize that while everything is new, that if you are blind hunting there really is a finite number of pictures worth taking. After awhile there REALLY ARE only so many warthog pictures that you need to take.
I always take a few of those red (or any color) bandannas with me. They work for everything from cleaning surfaces, holding a collection of something that you find, to providing an extra layer of warmth wrapped around your next, used as a napkin, or a cushion to lean you bow up against so that it doesn't get dirt, gravel or mud on the tip or in the string
A camera tripod. Seems like a luxury, but I usually take a point and shoot camera and then an SLR with lenses (maybe archaic at this point. There are many that are very light and can be packed easily. I set up the Nikon with the big lens out of the way and it cut down on a lot of movement while giving you much more stable pictures at a distance (this stability is even more an issue with small point and shoots that have tremendous magnification potential as any shake will blur the pictures.
Seems a little vain, but remember that you will be taking pictures of a life time, and that if you do take "hero pics " with game that has been taken you might want to look presentable and in some outfit that is not embarrassing. As important, is that many of those pictures that you take in Africa will be during the day and in bright sun. TAKE YOUR HAT OFF