I always wonder when I hear people saying they want to upgrade their certs: is ti actually going to help you in your career? Will anybody worry about which cert you have if you have several years' practical experience?
I feel there is definitely benefit to accrue indirectly, if not directly.
One learns aspects of the language (or framework as in this case) not very commonly used, which help lead to possibly more elegant but certainly distinct solutions that have better chance to stand out. Then of course one would hone their existing skills by studying and brushing up on material already in use so from pure knowledge perspective it's a win-win.
Oh, recruiters pulling up the resume may be a bonus, if at all!
I have only ever upgraded one of my 5 certs (the Java Programmer one from 5 to Java 8) and I wouldn't do it just for the paper but I find the learning process to be a good structured way of learning something new. My question could probably be better phrased as "is there enough new stuff from Spring 3 to Spring 5 to spend my time reading this book?".
I'm undecided if employers care too much, I certainly have never favoured someone with certs over someone without for a job.
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.
Joel Salatin has signs on his property that say "Trespassers will be Impressed!" Impressive tiny ad: