well i have found any ground up C lit is going to be for full blown computers and really confuses the subject
embedded c books like to narrow that down but it is still above what arduino does in its user friendly functions
I had no problems jumping into it, but I have been using systems similar to this for quite a while now, from what I remember when I started tho was just not understanding anything, to almost instantly understanding everything
one can pretty much figure out the functions by reading them, but the syntax or structure of the code is what throws a ton of people off, but pay attention to where ; and () and {} and [] are being used and it should start to pop for you pretty easily while exploring sample codes
and try not to start off with advanced ones either, go back and look at the blinking led script and this time focus on the markup rather than whats being done, you should be able to see block like structures of code forming in their {} brackets