First of all let me qualify my critique by saying that I use this book heavily and am grateful for it - every programmer should digest and drink in the material in this seminal and valuable book. However one must understand the boundaries of Design Patterns.
Object Oriented Programming has been the New Wave of the 80's and 90's.
The initial rah-rah over encapsulation-inheritance-polymorphism faded when their benefits were hard to extract.
The design patterns are one step above O-O. Heavily founded in the the main "tricks" behind the design patterns, are also the facets of O-O
2. dynamic binding (or polymorphism)
3. aggregation (or composition)
So in the future when there is the next new wave in software, I expect our paradigms to shift to something else.
In short, it is a great book, but it is not in the same league as (say) a Mathematics book which will stay current for a very, very long time.
(As a Christian myself, I liked John Vlissides unashamed quotes from the Bible on the first page
Joshua 24:15 "As for me and my house, we will serve the LORD")
How to read the book rapidly if you are a visually oriented person. I am a slow learner but was able to read this book in two hours:
1. First, understand intimately how the four "tricks" work, mentioned above.
2. Do not read in serial fashion from page 1 till end. Instead look at the structure diagram for a design pattern; meditate on it until you are blocked whereupon read the text to find the answer.