Every book has its own merit (well, I will backtrack by saying some technical books are really bad), though thanks for the recommendation. This E-Book is primarily an introduction using common/trendy technologies in practice. Not a deep-dive or theoretical studies of <name> distributed system.
Designing Data Intensive applications seemed to me a like a good balance between too academic and too practical. It was at perfect level of abstraction for me.
Seconded. One of the best technical books I've ever read. Wish more were like that.
Agreed, that is the best book O'Reilly ever put out. An example of how grown up Engineering books should be written.