"Compilers: Principles, Techniques, and Tools" or "The Dragon Book" as it is informally known was always recommended on compsci courses I have taken. It has a section within "Syntax Analysis" which covers context-free grammars.
In yet other words: I don't know what I don't know about grammar.
> The first edition in turn constituted a major revision of a previous textbook also written by Hopcroft and Ullman, entitled Formal Languages and Their Relation to Automata.
https://en.wikipedia.org/wiki/Introduction_to_Automata_Theor...
Used copy ordered.
Searching for that title also lead me to _Introduction to Formal Languages_ by Gyorgy E. Revesz, which also looks like a good fit and which Dover is currently printing as one of their reasonably-priced paperbacks!