Hello,
There are a lot of differences between Spring 3.0 and Spring 5.0, especially in the fact that the number of projects Spring has increased.
There is the new Reactive framework, support for new view technologies and Spring Boot is being used more and more because we're all moving to the cloud and microservices.
Is the certification worth upgrading? Depends what you need it for. If you need it for self confidence or because you are looking to change your job and want to have a shiner to attract recruiters, go ahead.
But nothing beats hands-on practical experience. And my book provides some insight into what that looks like too, because the sources that come with it integrate with modern build tools such as Gradle, containerized databases ( I have a few Oracle examples that work with an Oracle database container). The project is a multi-module with a practical configuration that you can use as inspiration for your own projects.
Truth is, you do not know the value of a book by its cover or just by the few answers I've given on this forum. It will become valuable if the knowledge aquired from it would help you solve Spring tasks easily at work, or design your applications to fully harness the power of the framework. But if you never use that knowledge, the book will be worthless to you.
Your end goal makes the book worth buying or not.
I know I should be trying to sell my book, but I reall do not be like one of those invasive Amazon or Facebook ads. I'm not gonna try to convince you to buy a book you might not need.
Cheers!