[1]: https://www.dol.gov/whd/regs/compliance/whdfs22.pdf
Schedule a workday to spend reading the book, or bill the company for taking up half your weekend.
If this worker is in a union, this is precisely the sort of issue to take up with the steward. Most programmers aren't, but apparently non-union workers already have an "an open and direct dialogue" with their managers, though it's kind of hard to tell if that's the case here since the manager is the one who can't seem to schedule one simple task for the employee.
My favorite is the lecture about sleep dept, about how two good nights sleep can reverse several days of sleep deprivation. Great. Work me 18-hours a day all week and leave it up to me to resolve it on the weekend. How convenient for the employer.