I would recommend against books, actually. They tend to get irrelevant very fast. I'd start with 1st and foremost reading
I Overview of Spring Framework and
III Core technologies here:
https://docs.spring.io/spring/docs/current/spring-framework-reference/html/
Then identifying areas of interest to you and going through appropriate guides here:
https://spring.io/guides
While doing guides it is very beneficial to go to reference docs again and read appropriate parts.
Spring's documentation is one of the best in the industry (at least in my experience).