This is one of those handy to have little books. While it is of limited use to those who are learning the language (it is too short and the material is not adequately described), it is very good to have around for those moments when your brain decides to go on holiday and you just cannot remember how to use strncpy!
It is of limited use for those learning as it is way too short to cram what learners require, plus it is not exactly up to speed with respects to the standard (every code example starts with just main()).
That said, the questions are just taxing enough to make you scratch your head and the short descriptions of the functions from the main headers are enough to prod you in the correct direction and at seven pounds, it is better than most books at four times the price!
The two strongest chapters in the book cover file operations and string handling with the string handling being far better than the file operations. The rest do the job, but just in no great depth.