There are so many books that cover the Arduino but most of them start with the Basics and then the IDE. Next they almost all have example projects.
I would like to find a book that covers all the commands, keywords, functions and whatever else the Arduino IDE can implement that are undocumented or hard to find info on. I find new ones in other peoples sketches, the forum or by accident when I type a word that turns orange in the IDE. (if orange is the correct colour, I'm partially colour blind)
Even if it's $100 it would be worth it instead of searching and finding minimal info on the net.