The book (if an assortment of unrelated Q&As could be called such) is an excellent way to test and enhance your knowledge of the C language.
I have many years of experience writing C code, and while most answers were obvious to me, there were some that completely threw me out of my comfort zone and provided ample food for thought.
I wholeheartedly recommend the book (or the free online version of it) to any C programmer with some prior experience who wants to know all the edge cases and "gotchas" of the language that are so frequently swept under the rug by many C programmers and book writers.