I would add to the list of things a mathematics textbook, along with a few physics/engineering ones, and agricultural books, maybe with some geology, biology and chemistry thrown in. Go for the ones that present matter really densely.
If you want more inspiration, look
here. This was a family in russia that cut themselves off from society for over 40 years. The things that they valued to most was tools, and you would likely want to bring an awful lot (as well as backups). Pretty much anyting electrical would not be suitable.
Also, keep in mind that we're pushing the reset button on society, and with an incredibly small population. That means that a lot of things which one would be used to from living in western society and the things that one would want to implement are simply not feasable. Marriage/family conventions, Universal education, and child labour rules would likely have to be abandoned. Given how small the population is, a formal set of laws would just not be worth it, but looking at the OP, that's something which may not be worth it at all.
If you're interestead in the long-term prospects of this society, then you basically need to spend the majority of your resources in the box trying to jump-start agriculture. The first few generations need to focus on sustainably increasing population as fast as possible - you've mentioned that your starting population is about 100, and you need that to be increased to five thousand at least before you get any significant cultural development.
Of course, going from 100 to 5000 is a fifty-fold increase, and this will take many of hundreds of years, especially to do so sustainably. That means that by the time your society is going to need any significant administrative system, the original population will be long dead, and there is a very high chance that however it is set up administratively at first, it will not resemble that at all. If you do want to have a cultural influence in the distant future, then best way to achieve it would probably be by setting up a religion. You don't need to prioritize methods of making physical records - any history you have can be preserved via oral tradition. Preserving the textbooks that you have, though, is exceedingly important. The agriculture ones alone would allow you to skip thousands and thousands of years of human development.
EDIT: Basically, apart from the box, you will be pretty much the same as a small tribe fifty thousand years ago. If we use past human development as a guide, you basically want to reach the
neolithic revolution as fast as possible - if you don't, then within a few hundred years the last remnants of any advantage you have will be erased. You therefore want to being in that box everything you need to speedrun human history - the agricultural stuff will let you jump to the neolithic revolution, and the physics and maths textbooks will let you try and speed through the twelve thousand years since. Don't spend too long trying to implement culture or administration for the first few generations, because it will likely go to shit before your society actually does anything.