ISTQB is a bad, bad thing. Reeeeeally bad thing. And here is why.
First of all, they certify something there are more than one opinion about. Something that has different approaches. Something that is poorly measurable since it depends on efficiency of decision making process. And decades of IQ testing and similar attempts to measure and control human brain and psyche proved it spectacularly inefficient.
Whatever you can read in ISTQB material is just an opinion and a book would suffice to share it. Unfortunately, royalties that only one or even several books can bring is nothing compared with certification system would bring. Basically, you bypass market competition by forcing people into buying books and paying for exams, and you do it by pressuring their employers into pressuring their employees.