Spring has become a huge universe! In fact, it has grown so much that any book you buy would be intimidating at first. Even well-known authors have difficulty in keeping it simple. They go into details of how to do the same thing in different ways (annotation, autowiring, etc, etc) that at the end the user is flabbergasted. Enter the "Just Spring" book. This book is exactly that, just Spring! Plain and simple. No noise, no dust.
In just 5 chapters, I learned a great deal about the fundamentals of Spring. Enough to get me started on enterprise level projects where I can build on my foundation. The power of this book lies in its simplicity. Most books on Spring are around 300-400 pages. This book is 62 pages. What can one learn in 62 pages, you might ask! Here's what I learned in one weekend - Basic mechanisms of dependency injection, bean life-cycle, bean instantiation techniques, autowiring techniques, event handling, JMS, and data integration. You might complain that it didn't cover bells and whistles like Spring Security, Spring Webflow, etc, etc, but these are add-ons that you can grasp easily once you get your foundation strong. I applaud the author for keeping it simple yet useful and O'Reilly for publishing it.