And it was really enlightening. I would heavily recommend it. It starts off by teaching different types of implementations of different parts of DBMS. Then goes on to teaching about how distributed systems deal with various problems.
The book is great but not what you seem to be looking for.
However, the book is definitely relevant to mobile applications. The backends for all the most popular apps are built with systems described in it.
Earlier this year, I read a few chapters of the book, and it was really abstract to me, so I stopped reading it.
On a whim, I had two developers teach me SQL and relational database theory. I spent a few weeks creating a few databases and connecting them to the front end to mimic real life application, before picking up the book again and the book made way more sense.